APPENDIX.

figure 95.

This machine may likewise be used to exhibit the falsity of the Ptolemaic system, which places the Earth in the centre, and supposes the sun and all the planets to revolve around it. For this purpose, the ball representing the Sun is removed, and placed on the wire or pillar which supports the Earth, and the ball representing the Earth is placed in the centre. It will then be observed, that the planets Mercury and Venus, being both within the orbit of the sun, cannot at any time be seen to go behind it, whereas, in the heavens we as often see them go behind as before the sun. Again, it shows that as the planets move in circular orbits about the central earth, they ought at all times to appear of the same magnitude; while, on the contrary, we observe their apparent magnitudes in the heavens to be very variable; Mars, for example, appearing sometimes nearly as largeas Jupiter, and at other times only like a small fixed star. Again, it is here shown that the planets may be seen at all distances from the sun; for example, when the sun is setting, Mercury and Venus, according to this arrangement, might be seen, not only in the south but even in the eastern quarter of the heavens—a phenomenon which was never yet observed in any age; Mercury never appearing beyond 27° of the Sun, nor Venus beyond 48°. In short, according to the system thus represented, it is seen, that the motions of the planets should all be regular, and uniformly the same in every part of their orbits, and that they should all move the same way, namely from west to east; whereas, in the heavens, they are seen to move with variable velocities, sometimes appearing stationary, and sometimes moving from east to west, and from west to east. All which circumstances plainly prove that the Ptolemaic cannot be the true system of the universe.

A Planetarium, such as that now described, might be constructed with brass wheel-work, for about 5 guineas. The brass wheel-work of one which I long since constructed cost about 3 guineas, and the other parts of the apparatus about 2 guineas more. The following are the prices of some instruments of this kind as made by Messrs. Jones, 30, Lower Holborn, London. ‘An Orrery, showing the motions of the Earth, Moon, and inferior planets, Mercury and Venus, by wheel-work, the board on which the instrument moves being 13 inches diameter, £4: 14s. 6d.’ ‘A Planetarium showing the motions of all the primary planets by wheel-work with 1½ inch or 3 inch papered globes,—according to the wheel-work and the neatness of the stands, from £7: 17s. 6d. to £10: 10s.’ ‘Ditto, with wheel-work to show the parallelism of the Earth’s axis, the motions of the Moon, her phases, &c., £18: 18s.’ ‘Ditto, with wheel-work, to show the earth’s diurnal motion, on a brass stand in mahogany case, £22: 1s.’ ‘A smallTellurian, showing the motion of the Earth and Moon, &c., £1: 8s.’

The following is a description of the most complete and accurate planetarium I have yet seen. The calculations occupied more than eight months. For this article I am indebted to my learned and ingenious friend Dr. Henderson, F.R.A.S., who is known to many of my readers by his excellent astronomical writings.

figure 96.

Section of the wheel-work of a Planetarium for shewing with the utmost degree of accuracy the mean tropical revolutions of the planets round the sun, calculated by E. Henderson, LL.D. &c.

In the above section the dark horizontal lines represent the wheel-work of the Planetarium, and the annexed numerals, the numbers of teeth in the given wheel. The machine has three axes or arbors, indicated by the letters A, B, C.—Axis ‘C,’ the ‘Yearly axis,’ is assumed to make one revolution in 365.242,236 days, or, in 365 days 5h48m49.19sand is furnished with wheels 17,44, 54, 36, 140, 96, 127, 86, which wheels are all firmly riveted to said axis, and consequently they turn round with it in the same time. Axle ‘B’ is a fixture; it consists of a steel rod, on which a system of pairs of wheels revolve; thus wheels 40 and 77 are made fast together by being riveted on the same collet represented by the thick dark space between them, as also of the rest: the several wheels on this axis may be written down thus;40/77,49/129,20/94,79/81, 30,27/50,41/65,59/65, 96,77/47,67/42. On axis A a system of wheels, furnished with tubes revolve, and these tubes carry horizontal arms, supporting perpendicular stems with the planets. The wheels on this axis are 173,117/190, 111, 119,122/130,123/127, 83, 239, 96, 128, 72. From the following short description the nature of their several actions will, it is presumed, be readily understood—viz.,

MERCURY’S PERIOD.

On the axis ‘C’ at the bottom is wheel 86, which turns round in 365 days 5h48m49.19s, this wheel impels a small wheel of 22 teeth, to which is made fast to wheel 67, both revolving together at the foot of axis B; wheel 67 drives a wheel of 72 once round in the period of 87 days, 23h14m36.1s: this last mentioned wheel has a long tube, which turns on the steel axis A, and carries a horizontal arm with the planet Mercury round the sun in the time above noted.

VENUS’S PERIOD.

On axis ‘C’ is wheel 127, which drives wheel 47, to which is riveted a wheel of 77 teeth, which impels a wheel of 128 teeth on axis A, andcauses it to make a revolution in 224 days, 16h41m31.1s, and is furnished with a tube, which revolves over that of Mercury and ascends through the cover of the machine, and bears an arm on which is placed a small ball representing this planet in the time stated.

THE EARTH’S PERIOD.

The motion of the earth round the sun is simply effected as follows—the assumed value of axis ‘C;’ the ‘Yearly axis’ is 365 days 5h48m49.19s; hence a system of wheels having the same numbers of teeth, or at all events, the first mover, and last wheel impelled must be equal in their numbers of teeth; in this machine three wheels are employed, thus; a wheel having 96 teeth is made fast to the Yearly axis C and of course moves round with it in a mean solar year, as above noted, this wheel impels another wheel of 96 teeth, on axis B, and this in its turns drives a third wheel of 96 teeth on axis A, and is furnished with a long tube which revolves over that of Venus, and ascends above the cover-plate of the machine, and bears a horizontal arm which supports a small terrestrial globe, which revolves by virtue of said wheels once round the sun in 365 days 5h48m49.19s.

MARS’ PERIOD.

The revolution of this planet is effected as follows—a wheel of 140 teeth is made fast to the yearly axisC, and drives on axis B a wheel of 65 teeth, to which is fixed a wheel of 59 teeth, which impels a large wheel of 239 teeth on axis A once round the sun in 686 days 22h18m33.6s, this last-mentioned wheel is also furnished with a tube which revolves over that of the earth, and carries a horizontal arm bearing the ball representing Mars, and causes it to complete a revolution round the sun in the period named.

THE ASTEROIDS.VESTA’S PERIOD.

The period of Vesta is accomplished thus, viz. On the Yearly axis C, is made fast a wheel of 36 teeth, which drives a wheel of 65 teeth on axis B, to which is fixed a wheel of 41 teeth, which impels a wheel of 83 teeth on axis A, once round in 1336 days 0h21m19.8s: The tube of which last wheel ascends on that of Mars, and like the rest bears an arm supporting a ball representing this planet.

JUNO’S PERIOD.

For the revolution of Juno, the yearly axis C is furnished with a wheel of 54 teeth, which impels a wheel of 50 teeth on axis B, to which is made fast a wheel of 27 teeth which turns a wheel of 127 teeth on axis A, once round in 1590 days 17h35m2.7s, and the tube of which ascends on that of Vesta, and supports a horizontal arm which carries a small ball representing this planet in the period named.

CERES’ PERIOD.

The revolution of Ceres is derivedfrom the period of Juno, because wheel-work taken from the unit of a solar year was not sufficiently accurate for the purpose, therefore on Juno’s wheel of 127 teeth is fixed a wheel of 123 teeth, which drives a thick little bevel sort of wheel of 30 teeth on axis B: the reason of this small wheel being bevelled is to allow its teeth to suit both wheels123/130; wheel 30 drives wheel 130, on axis A once round in 1681 days, 6h17m22.4sand the tube of wheel 130 turns on the tube of Juno, and ascends in a similar manner with the rest and carries an horizontal arm supporting a small ball representing this planet, and is caused to revolve round the Sun in the above mentioned period (the period of Ceres to that of Juno is as 130 is to 123; hence the wheels used.)

PALLAS’S PERIOD.

The Period of Pallas could not be derived from the solar year with sufficient accuracy, and recourse was had to an engrafted fraction on the period of Ceres, thus. On wheel 130 of Ceres is made fast a wheel of 122 teeth, which drives a wheel of 81 teeth on axis B, to which is fixed a wheel 79 which impels a wheel of 119 teeth on axis A, and is furnished with a tube which ascends, and turns on that of Ceres, and supports a horizontal arm, which bears a small ball representing this planet, which by virtue of the abovetrain of wheels is caused to complete a revolution round the Sun in 1681d10h28m25.1s.

JUPITER’S PERIOD.

The motion of this planet is derived from the period of a solar year; from the ‘yearly axis’ thus, on this axis is made fast a wheel of 44 teeth which turns a wheel of 94 teeth on axis B, to which is riveted a small wheel of 20 teeth, which impels a wheel on axis A having 111 teeth, which is furnished with an ascending tube which revolves over that of Pallas, and bears an horizontal arm which supports a ball representing this planet, which by the said train of wheels is caused to revolve round the Sun in 4330d14h39m35.7s.

SATURN’S PERIOD.

The periodic revolution of Saturn is also taken from the solar year—viz., a small wheel of 17 teeth is fixed to the ‘yearly axis’ near its top, and drives a wheel of 129 teeth on axis B, to which is made fast a wheel of 49 teeth, which turns a wheel of 190 teeth on axis A, whose tube ascends and revolves on that of Jupiter’s tube, and supports an arm, having a ball representing Saturn and its rings, and which by the train of wheels is caused to perform a revolution round the sun in the period of 10746d19h16m50.9s.

URANUS’S PERIOD.

The revolution of this planet could not be attained with sufficient accuracy from the period of a solaryear—the period is engrafted on that of Saturn’s, thus, a wheel of 117 teeth is made fast to wheel 190 of Saturn, and consequently revolves in Saturn’s period. This wheel of 117 teeth drives a wheel on axis B, having 77 teeth, to which is fixed a wheel of 40 teeth, which turns on axis A, a large wheel of 173 teeth, whose tube ascends and revolves over that of Saturn, and carries a horizontal arm which supports a ball representing this planet, which is caused to complete its revolution by such a train of wheels in the period of 30589d8h26m58.4s. Such is a brief description of the motions of this comprehensive and very accurate machine.

The axis A, on which the planetary tubular wheels revolve, performs a rotation in 25 days 10 hours, by virtue of the following train of wheels,61/14+70/12of 24 hours, that is, a pinion of 14 is assumed to revolve in 24 hours, and to drive a wheel of 61 teeth, to which is fixed a pinion of 12, which turns the wheel 70 in the period noted; to this wheel-axis, it is made fast, and by revolving with it, exhibits the Sun’s rotation.

DIURNAL HAND.

The machine is turned by a handle or winch, which is assumed to turn round in 24 hours, and from this rotation of 24 hours a train of wheel-work is required to cause the ‘yearly axis’ C, to turn once round in 365d5h48m49.19s, which is effected in the following manner—viz, the train foundby the process of the reduction of continuous fractions is61/14+144/18+211/23that is, in the train for turning the sun, the same pinion 14 turns the same wheel 61, and turns a pinion of 18 leaves, to which is fixed a wheel of 144 teeth, having a pinion of 23 leaves, which impels a large wheel of 241 teeth once round in 365.242236dor 365d5h48m49.19s, this last-mentioned wheel of 241 teeth is made fast to the under part of the ‘yearly axis’ C at D, the handle having a pinion of 14 leaves therefore, and transmitting its motion through the above train, causes the yearly axis to revolve in the same period.

REGISTRATING DATES.

The planetarium is also furnished with a system of wheels for registrating dates for either 10,000 years past or to come, the arrangement is not shewn in the engraving (to prevent confusion) but it might be shortly described thus:—Near the top of the yearly axis is a hooked piecee, which causes the tooth of a wheel of 100 teeth to start forward yearly, consequently 100 starts of said wheel will cause it to revolve in 100 solar years, and it has a hand which points on a dial on the cover of the machine the years; thus for the present year this hand will be over the number 45. This last-named wheel of 100 teeth has a pin which causes a tooth of another wheel of 100 teeth to start once in 100 years,hence this last wheel will complete one revolution in 10,000 years, and it is for this purpose the former index or hand moves over a number yearly. The second index will pass over a number every 100 years—for the present year the second hand or index will be over the number 18, and will continue over it until the first index moves forward to 99, then both indexes will move at one time, viz., the first index to 00 on the first concentric circle of the dial, and the second index to 19, denoting the year 1900, and so of the rest. By the ecliptic being divided in a series of four spirals, the machine makes a distinction between common and leap years, and indicates the common year as containing 365 days, and the leap-year 366 days, by taking in a day in February every fourth year; thus for any given period for 10,000 years past or to come, the various situations and aspects of the planets may be ascertained by operating with this machine, and this for thousands of years without producing a sensible error either in space or time. This planetarium wheel-work is enclosed in an elegant mahogany box of twelve sides—is about 5 feet in diameter by 10 inches in depth; at each of the twelve angles, or sides, small brass pillars rise and support a large Ecliptic circle on which are engraventhe signs, degrees and minutes of the Ecliptic—the days of the month, &c. This mahogany box with the wheel-work is supported by a tripod stand three feet in height, and motion is communicated to the several balls representing the planets by turning the handle as before described. A Planetarium of this complicated sort, costs sixty guineas.

The following is a tabular view of the wheel-work, periods, &c.

In the month of October last year, Dr. Henderson made a series of calculations for a new Planetarium for the use of schools. It shows with considerable accuracy for 700 days, the mean tropical revolutions of the Planets round the sun—the machine consists of a system of brass wheels peculiarly arranged, and is enclosed in a circular case three feet in diameter, the top of which has the signs and degrees of the ecliptic laid down on it, as also the days of the months, &c. This Planetarium costs only 45s. or on a tripod stand, table-high, 55s.; the machine is put in motion by a handle on the outside. To the teachers and others connected with education this Planetarium must be of great importance, for without a proper elucidation of the principles of astronomy, that of Geography must be but confusedly understood. This Planetarium is at present made by Mr. Dollond, 9, White Conduit Grove, Islington, London.

TheTellurianis a small instrument which should be used in connection with the Planetarium formerly described. This instrument is intended to show the annual motion of the earth, and the revolution of the moon around it. It also illustrates the moon’s phases, and the motion of her nodes, the inclination of the Earth’s axis, the causes of eclipses, the variety of seams, and other phenomena. It consists of about eight wheels, pinions and circles. A small instrument of this description may be purchased for about one pound eight shillings, as stated in the note, page 527.

figure 97.

The striking and singular phenomenon connected with the planet Saturn—though now ascertained beyond dispute to be a Ring, or Rings, surrounding its body at a certain distance—was a subject of great mystery, and gave rise to numerous conjectures and controversies, for a considerable time after the invention of the telescope by which it was discovered. Though it was first discovered in the year 1610, it was nearly 50 years afterwards, before its true form and nature were determined. Galileo was the first who discoveredanything uncommon connected with Saturn: through his telescope he thought he saw that planet appear like two smaller globes on each side of a larger one; and after viewing the planet in this form for two years, he was surprised to see it becoming quite round, without its adjoining globes, and some time afterwards to appear in the triple form. This appearance is represented in fig. 1 of the above engraving. In the year 1614, Scheiner, a German astronomer, published a representation of Saturn, in which this planet is exhibited as a large central globe, with two smaller bodies, one on each side, partly of a conical form, attached to the planet and forming a part of it, as shown fig. 2. In the year 1640 and 1643, Ricciolus, an Italian mathematician and astronomer, imagined he saw Saturn as represented in fig. 3. consisting of a central globe, and two conical shaped bodies completely detached from it, and published an account of it corresponding to this view. Hevelius, the celebrated astronomer of Dantzig, author of theSelenographiaand other works, made many observations on this planet about the years 1643, 1649 and 1650, in which he appears to have obtained different views of the planet and its appendages, gradually approximating to the truth, but still incorrect. These views are represented in figures 4, 5, 6, and 7. Fig. 4 nearly resembles two hemispheres, one on each side of the globe of Saturn. The other figures very nearly resemble the extreme parts of the ring as seen through a good telescope, but he still seems to have considered them as detached from each other as well as from Saturn. Figures 8 and 9 are views given by Ricciolus at a period posterior to that in which he supposed Saturn and his appendages in the form delineatedin fig. 3. In these last delineations the planet was supposed to be enclosed in an elliptical ring, but this ring was supposed to befixedto its two opposite sides.

Fig. 10, is a representation by Eustachius Divini, a celebrated Italian optician at Bologna. The shades represented on Saturn and the elliptical curve are incorrect, as this planet presents no such shadowy form. The general appearance here presented is not much unlike that which the ring of Saturn exhibits, excepting that at the upper side the ring should appear covering a portion of the orb of Saturn. But Divini seems to have conceived that the curve on each side was attached to the body of Saturn. For when Huygens published his discovery of the ring of Saturn in 1659, Divini contested its truth, because he could not perceive the ring through his own telescopes; and he wrote a treatise on the subject in opposition to Huygens, in 1660, entitled ‘Brevis Annotatio in Systema Saturninum.’ Huygens immediately replied to him, and Divini wrote a rejoinder in 1661.—Fig. 11 is the representation given by Francis Fontana, a Neapolitan astronomer. This figure represents Saturn as having two crescents, one on each side, attached to its body, with intervals between the planet and the crescents. Fig. 12 is a view delineated by Gassendus, a celebrated French philosopher. It represents the planet as a large ellipsoid, having a large circular opening near each end, and, if this representation were the true one, each opening would be at least 30,000 miles in diameter. Fig. 13, which is perhaps the most singular of the whole, is said to be one of the view’s of this planet given by Ricciolus. It represents two globes—each of which, in the proportion they here bear to Saturn, must be more thanthirty thousand miles in diameter. These globes, were conceived as being attached to the body of Saturn by curves or bands, each of which, in the proportion represented, must have been at least 7000 miles in breadth, and nearly 40,000 miles long. This would have exhibited the planet Saturn as a still more singular body than what we have found it to be; but no such construction of a planet has yet been found in the universe, nor is it probable that such a form of a planetary body exists.

It is remarkable that only two general opinions should have been formed respecting the construction of Saturn—as appears from these representations—either that this planet was composed of three distinct parts, separate from each other,—or that the appendage on each side wasfixedto the body of the planet. The idea of a ring surrounding the body of the planet, at a certain distance from every part of it, seems never to have been thought of till the celebrated Huygens, in 1655, 1656 and 1657, by numerous observations made on this planet, completely demonstrated that it is surrounded by a solid and permanent ring, which never changes its situation, and, without touching the body of the planet, accompanies it in its revolution around the sun. As the cause of all the erroneous opinions above stated was owing to the imperfection of the telescopes which were then in use, and their deficiency in magnifying power,—this ingenious astronomer set himself to work in order to improve telescopes for celestial observations. He improved the art of grinding and polishing object-glasses, which he finished with his own hands, and produced lenses of a more correct figure, and of a longer focal distance than what had previously been accomplished. He first constructeda telescope 12 feet long, and afterwards one 23 feet long, which magnified about 95 times; whereas Galileo’s best telescope magnified only about 33 times. He afterwards constructed one 123 feet long, which magnified about 220 times. It was used without a tube, the object-glass being placed upon the top of a pole and connected by a cord with the eye-piece. With such telescopes this ingenious artist and mathematician discovered the fourth satellite of Saturn, and demonstrated that the phenomenon, which had been so egregiously misrepresented by preceding astronomers, consisted of an immense ring surrounding the body, and completely detached from it. His numerous observations and reasonings on this subject were published in Latin, in 1659, in a quarto volume of nearly 100 pages, entitled ‘Systema Saturnium, sive de causis mirandorum Saturni Phenomenôn, et Comite ejus Planeta Nova,’ from which work the figures and some of the facts stated above have been extracted.

From the period in which Huygens lived till the time when Herschel applied his large telescopes to the heavens, few discoveries were made in relation to Saturn. Cassini, in 1671, discovered the fifth satellite of this planet; in 1672, the third; and the first and second in March, 1684. In 1675, Cassini saw the broad side of its ring bisected quite round by a dark elliptical line, of which the inner part appeared brighter than the outer. In 1722, Mr. Hadley, with his 5 feet Newtonian Reflector observed the same phenomenon, andperceived that the dark line was stronger next the body, and fainter towards the upper edge of the ring. Within the ring he also discovered two belts across the disk of Saturn. But it does not appear that they had any idea that this dark line was empty space separating the ring into two parts. This discovery was reserved for the late Sir W. Herschel, who made numerous observations on this planet, and likewise ascertained that the ring performs a revolution round the planet in ten hours and thirty minutes.

Of late years, some observers have supposed that the exterior ring of Saturn is divided into several parts, or, in other words, that it consists of two or more concentric rings. The following are some of the observations on which this opinion is founded. They are chiefly extracted from Captain Kater’s Paper on this subject, which was read before the Astronomical Society of London.

The observations, we are told, were made in the years 1825 and 1826, and remained unpublished, from a wish on the part of the observer to witness the appearances again. The planet Saturn has been much observed by Captain Kater, for the purpose of trying the light, &c., for which the ring and satellites are good tests. The instruments which were employed in the present investigations were two Newtonian Reflectors—one by Watson, of 40 inches focus and 6¼ aperture; and another by Dollond, of 68 inches focus, and 6¾ aperture. The first, under favourable circumstances, gave a most excellent image, the latter is a very good instrument. The following are extracts from the author’s journal.

Nov. 25, 1825.—The double ring beautifully defined, perfectly distinct all around, and the principalbelts well seen. I tried many concave glasses, and found that the image was much sharper than with convex eye-glasses, and the light apparently much greater. Dollond, 259, the best power, 480, a single lens, very distinct.Nov. 30, the night very favourable, but not equal to the 25th. The exterior ring of Saturn is not so bright as the interior, and the interior is less bright close to the edge next the planet. The inner edge appears more yellow than the rest of the ring, and nearer in colour to the body of the planet.Dec. 17.—The evening extremely fine. With Dollond, I perceived the outer ring of Saturn to be darker than the inner, and the division of the ring all around with perfect distinctness; but with Watson I fancied that I sawthe outer ring separated by numerous dark divisions extremely close, one stronger than the rest, dividing the ring about equally. This was seen with my most perfect single eye-glass power. A careful examination of some hours confirmed this opinion.—Jan. 16and 17, 1826.—Captain Kater believed that he saw the divisions with the Dollond, but was not positive. Concave eye-glasses found to be superior to convex.Feb. 26, 1826.—The division of the outer ring not seen with Dollond. On the 17th Dec., when the divisions were most distinctly seen, Captain Kater made a drawing of the appearance of Saturn and his rings. The phenomena were witnessed by two other persons on the same evening, one of whom saw several divisions in the outer ring, while the other saw one middle division only; but the latter person was short-sighted, and unaccustomed to telescopic observations. It may be remarked, however, that these divisions were not seen on other evenings, which yet were considered very favourable for distinct vision.

It is said that the same appearances were seen by Mr. Short, but the original record of his observations cannot be found. In Lalande’sAstronomy(3rd edition, article 3351,) it is said, ‘Cassini remarked that the breadth of the ring was divided into two equal parts by a dark line having the same curvature as the ring, and theexteriorportion was the less bright. Shorttoldme that he observed still more singular phenomena with his large telescope of 12 feet. The breadth of the ansæ, or extremities of the ring; was, according to him, divided into two parts,—an inner portion without any break in the illumination, and an outer divided by several lines concentric with the circumference; which would lead to a belief,that there are several rings in the same plane.’ De Lambre and Birt severally state that Short saw the outer ring divided, probably on the authority of Lalande. In Brewster’sFerguson’s Astronomy, vol. ii, p. 125, 2nd edition, there is the following note on this subject. ‘Mr. Short assures us, that with an excellent telescope, he observed the surface of the ring divided by several dark concentric lines, which seem to indicate a number of rings proportional to the number of dark lines which he perceived.’

In Dec. 1813, at Paris, Professor Quetelet saw the outer ring divided with the achromatic telescope of 10 inches aperture, which was exhibited at the exposition. He mentioned this the following day to M. de la Place, who observed, that ‘those or even more divisions, were conformable to the system of the world.’ On the other hand the division of the outer ring was not seen by Sir W. Herschel in 1792, nor by Sir J. Herschel in 1826, nor by Struve in the same year; and on several occasions when the atmospheric conditions weremost favourable, it has not been seen by Captain Kater. It has been remarked by Sir W. Herschel, Struve and others, that the exterior ring is much less brilliant than the interior. And it is asked, may not this want of light in the outer ring arise from its having a very dense atmosphere? and may not this atmosphere in certain states admit of the divisions of the exterior ring being seen, though, under other circumstances, they remain invisible? The above observations are said to have been confirmed by some recent observations by Decuppis at Rome, who announced, some years ago, that Saturn’s outer ring is divided into two or three concentric rings.

Some of the observations stated above, were they perfectly correct, would lead to the conclusion that Saturn is encompassed with a number of rings, concentric with and parallel to each other. But while such phenomena as described above are so seldom seen, even by the most powerful telescopes and the most accurate observers, a certain degree of doubt must still hang over the subject; and we must suspend our opinion on this point, till future observations shall either confirm or render doubtful those to which we have referred. Should the Earl of Rosse’s great telescope, when finished for observation, be found to perform according to the expectations now entertained, and in proportion to its size and quantity of light, we shall expect that our doubts will be resolved in regard to the supposed divisions of the ring of Saturn.

This telescope, the largest and most magnificent that ever was attempted, reflects the greatest honour on the genius, the inventive powers, and the scientific acquirements of its noble contriver, as well as on the elevated station in which he is placed. With rank and fortune, and every circumstance that usually unfit men for scientific pursuit, he has set a bright example to his compeers of the dignity and utility of philosophical studies and investigations, and of the aids they might render to the progress of science, were their wealth and pursuits directed in a proper channel.

Previously to his Lordship’s attempting the construction of his largest—or ‘Monster Telescope,’ he had constructed one with a speculum of 3 feet in diameter, which was considered one of the most accurate and powerful instruments that had ever been made, not excepting even Sir W.Herschel’s forty-feet Reflector. In the account of this telescope, published in the Philosophical Transactions for 1840, his Lordship speaks of the possibility of a speculum of six feet in diameter being cast. At that time, it was considered by some as little short of a chimera to attempt the construction of such a monstrous instrument. But the idea no sooner occurred to this ingenious and persevering nobleman than he determined to put it to the test, and the result has been attended with complete success. The materials of which this speculum is composed arecopperandtin, united very nearly in their atomic proportions, namely, copper 126.4 parts, to tin 58.9 parts. This compound has a specific gravity of 8.8, and it is found to preserve its lustre with more splendor, and to be more free from pores than any other. A foundry was constructed expressly for the purpose of casting the speculum. Its chimney built from the ground was 18 feet high, and 16½ square at the base, tapering to four at the top. At each of its sides, communicating with it by flue, was sunk a furnace 8 feet deep, and 5½ square, with a circular opening 4 feet in diameter. About seven feet from the chimney was erected a large crane, with the necessary tackle for elevating and carrying the crucibles from the furnace to the mould, which was placed in a line with the chimney and crane, and had three iron baskets supported on pivots hung round it; and four feet farther on was the annealing oven. The crucibles which contained the metal were each 2 feet in diameter, 2½ deep, and together weighed one ton and a half; they were of cast iron and made to fit the baskets at the side of the mould. These baskets were hung on wooden uprights or pivots, to one of these on each side was attached a lever,by depressing which it might be turned over, and the contents of the crucible poured into the mould. The bottom of the mould was made by binding together tightly layers of hoop-iron, and turning the required shape on them edgewise. This mould conducted the heat away through the bottom, and cooled the metal towards the top in infinitely small layers, while the interstices, though close enough to prevent the metal from escaping, were sufficiently open to allow the air to penetrate. This bottom was six feet in diameter and 5½ inches thick, and was made perfectly horizontal by means of spirit levels, and was surrounded by a wooden frame; a wooden pattern, the exact size of the speculum, being placed on the iron; sand was well packed between it and the frame, and the pattern was removed. Each of the crucibles containing the melted metal was then placed in its basket, and every thing being ready for discharging their contents, they were at the same instant turned over, and the mould being filled, the metal in a short time safely set into the required figure. Whilst it was red hot, and scarcely solid, the frame-work was removed, and an iron ring connected with a bar which passed through the oven, being placed round it, it was drawn in by means of a capstan at the other side, on a railroad, when charcoal being lighted in the oven, and turf fires underneath it, all the openings were built up, and it was left for sixteen weeks to anneal. It was cast on the 13th of April, 1842, at 9 o’clock in the evening. The crucibles were ten hours heating in the furnaces before the metal was introduced, which in about ten hours more was sufficiently fluid to be poured. When the oven was opened the speculum was found as perfect as when it entered it. It was then removed to the grindingmachine, where it underwent that process, and afterwards was polished, without any accident having occurred.

This speculum weighedthree tons, and lost about one eighth of an inch in grinding. Lord Rosse has since cast another speculum of the same diameter four tons in weight. He can now, with perfect confidence, undertake any casting, so great an improvement has the form of mould which he has invented proved. The speculum was placed on an equilibrium bed, composed of nine pieces resting on points at their centres of gravity; the pieces were lined with pitch and felt, before the speculum was placed on them. The speculum box is also lined with felt and pitched; this prevents any sudden change of temperature affecting the speculum by means of the bad conducting power of the substances employed. A vessel of lime is kept in connection with the speculum-box to absorb the moisture, which otherwise might injure the mirror. The process of grinding was conducted under water, and the moving power employed was a steam-engine of three-horse power. The Polisher is connected with the machinery by means of a large ring of iron, which loosely encircles it; and instead of either the speculum or the polisher being stationary, both move with a regulated speed; the ring of the polisher, and therefore the polisher itself, has a transverse and a longitudinal motion; it makes 80 strokes in the minute, and 24½ strokes backward and forward for every revolution of the mirror, and at the same time 172/100strokes in the transverse direction. The extent of the latter is27/100of the diameter of the speculum. The substance made use of to wear down the surface was emery and water, a constant supply of these waskept between the grinder and the speculum. The Grinder is made of cast iron, with grooves cut lengthways, across and circularly on its face. The polisher and speculum have a mutual action upon each other; in a few hours, by the help of the emery and water, they are both ground truly circular, whatever may have been their previous defects. The grinding is continued till the required form of surface is produced; and this is ascertained in the following manner. There is a high tower over the house in which the speculum is ground, on the top of which is fixed a pole, to which is attached the dial of a watch; there are trap doors which open, and by means of a temporary eye-piece, allow the figure of the dial to be seen in the speculum brought to a slight polish. If the dots on the dial are not sufficiently well-defined, the grinding is continued; but if they appear satisfactorily, the polishing is commenced. It required six weeks to grind it to a fair surface. The polisher was cut into grooves, to prevent the abraded matter from accumulating in some places more than in others—a thin layer of pitch was spread over it, it was smeared over with rouge and water, and a supply of it kept up till the machinery brought it to a fine black polish. The length of time employed for polishing the 3 feet speculum was six hours.48

This large telescope is now completed, or nearly so. The tube is 56 feet long, including the speculum box, and is made of deal, one inch thick, hooped with iron. On the inside, at intervals of8 feet, there are rings of iron 3 inches in depth and 1 inch broad, for the purpose of strengthening the sides. The diameter of the tube is 7 feet. It is fixed to mason-work, in the ground, to a large universal hinge which allows it to turn in all directions. At 12 feet distance, on each side, a wall is built, 72 feet long, 48 high on the outer side, and 56 on the inner—the walls being 24 feet distant from each other, and lying exactly in the meridional line. When directed to the south, the tube may be lowered till it become almost horizontal; but when pointed to the north, it only falls till it is parallel with the earth’s axis, pointing then to the pole of the heavens. Its lateral movements take place only from wall to wall, and this commands a view for half an hour on each side of the meridian—that is, the whole of its motion from east to west is limited to 15 degrees. At present it is fitted up in a temporary way to be used as a Transit instrument; but it is ultimately intended to connect with the tube-end galleries, machinery which shall give an automaton movement, so that the telescope shall be used as an Equatorial Instrument. All the works connected with this instrument are of the strongest and safest kind; all the iron-work was cast in his Lordship’s laboratory by men instructed by himself, and every part of the machinery was made under his own eye, by the artizans in his own neighbourhood, and not a single accident worth mentioning happened during the whole proceeding.

The expence incurred by his Lordship in the erection of this noble instrument was not less thantwelve thousand pounds! besides the money expended in the construction of the telescope of three feet diameter. Sufficient time has not yet beenafforded for making particular observations with this telescope; but from slight trials which have been made, even under unfavourable circumstances, it promises important results. Its great superiority over every telescope previously constructed consists in the great quantity of light it reflects, and the brilliancy with which it exhibits objects even when high powers are applied. It has a reflecting surface of 4,071 square inches, while that of Herschel’s 40-feet telescope had only 1811 square inches on its polished surface, so that the quantity of light reflected from the speculum is considerably more than double that of Herschel’s largest reflector. This instrument has already exceeded his Lordship’s expectations. Many appearances before invisible in the Moon, have been perceived, and there is every reason to expect that new discoveries will be made by it in theNebulæ, double and triple stars, and other celestial objects. The following is an extract of a communication from Sir James South, on this subject, addressed to the Editor of the ‘Times.’ ‘The leviathan telescope on which the Earl of Rosse has been toiling upwards of two years, although not absolutely finished, was on Wednesday last directed to the Sidereal Heavens. The letter which I have this morning received from its noble maker, in his usual unassuming stile, merely states, that the metal only just polished, was of a pretty good figure, and that with a power of 500, the nebula known as No. 2., of Messier’s catalogue, was even more magnificent than the nebula, No. 13 of Messier, when seen with his Lordship’s telescope of 3 feet diameter, and 27 feet focus. Cloudy weather prevented him from turning the leviathan on any other nebulous object. Thus, then, we have all danger of the metal breakingbefore it could be polished, overcome. Little more, however, will be done with it for some time, as the Earl is on the eve of quitting Ireland for England to resign his post at York as President of the British Association. I look forward with intense anxiety to witness its first severe trial, when all its various appointments shall be completed, in the confidence that those who may then be present, will see with it what man has never seen before. The diameter of the large metal is 6-feet, and its focus 54 feet; yet the immense mass is manageable by one man. Compared with it, the working telescopes of Sir William Herschel, which in his hands conferred on astronomy such inestimable service, and on himself astronomical immortality, were but playthings.’

The following is a more recent account of observations made by this telescope, chiefly extracted from Sir James South’s description of this telescope, inserted in theTimesof April 16th, 1845, and the ‘Illustrated London News’ of April 19.

‘The night of the 5th of March, 1845, was the finest I ever saw in Ireland. Many nebulæ were observed by Lord Rosse, Dr. Robinson and myself. Most of them were for the first time since their creation, seen by us as groups or clusters of stars; while some, at least to my eyes, showed no such resolution. Never, however, in my life did I see such glorious sidereal pictures as this instrument afforded us. Most of the nebulæ we saw I certainly have observed with my own large achromatic; but although that instrument, as far as relates to magnifying power, is probably inferior to no one in existence, yet to compare these nebulæ, as seen with it and the 6-feet telescope, is like comparing, as seen with the naked eye, the dinginess of the planet Saturn to the brilliancyof Venus. The most popularly-known nebulæ observed this night were the ring nebulæ in theCanes Venatici, or the 51st of Messier’s catalogue, which was resolved into stars with a magnifying power of 548, and the 94th of Messier, which is in the same constellation, and which was resolved into a large globular cluster of stars, not much unlike the well-known cluster in Hercules, called also 13th Messier.’ Perfection of figure, however, of a telescope, must be tested, not by nebulæ, but by its performance on a star of the first magnitude. If it will, under high power, show the star round and free from optical appendages, we may safely take it for granted it will not only show nebulæ well, but any other celestial object as it ought. To determine this point, the telescope was directed toRegulus, with the entire aperture, and a power of 800, and ‘I saw’ says Sir James, ‘with inexpressible delight, the star free from wings, tails or optical appendages; not indeed like a planetary disk, as in my large achromatic, but as a round image resembling voltaic light between charcoal points; and so little aberration had this brilliant image, that I could have measured its distance from, and position with any of the stars in the field with a spider’s line micrometer, and a power of 1,000, without the slightest difficulty; for, not only was the large star round, but the telescope, although in the open air, and the wind blowing rather fresh, was as steady as a rock.’

‘On subsequent nights, observations of other nebulæ, amounting to some 30 or more, removed most of them from the list of nebulæ, where they had long figured, to that of clusters; while some of these latter, more especially 5 Messier, exhibited a sidereal picture in the telescope such asman before had never seen, and which for its magnificence baffles all description. Several double stars were seen with various apertures of the telescope, and with powers between 360 and 800; and as the Earl had told us before we should,—before the speculum was inserted in the tube, in consequence of his having been obliged to quit the superintendence of the polishing at the most critical part of the process,—we found that a ring of about 6 inches broad, reckoning from the circumference of the speculum, was not perfectly polished, and tothatthe little irradiation seen about Regulus was unquestionably referable. The only double stars of the 1st class which the weather permitted us to examine with it were Xi Ursæ Majoris, and Gamma Virginis, which I could have measured with the greatest confidence. D’Arrest’s comet we observed on the 12th of March, with a power of 400, but nothing worthy of notice was detected. Of the Moon, a few words must suffice. Its appearance in my large achromatic of 12 inches aperture is known to hundreds of readers; let them then imagine that with it they lookatthe moon, whilst with Lord Rosse’s 6 feet they lookinto it, and they will not form a very erroneous opinion of the performance of the Leviathan. On the 15th of March, when the moon was 7 days old, I never saw her unilluminated disk so beautifully, nor her mountains so temptingly measurable. On my first looking into the telescope, a star of about the 7th magnitude was some minutes of a degree from the moon’s dark limb, and its occultation by the moon appeared inevitable. The star, however, instead of disappearing the moment the moon’s edge came in contact with it, apparently glided on the moon’s dark face, as if it had been seen through a transparentmoon, or as if the star were between me and the moon. It remained on the moon’s disk nearly two seconds of time, and then disappeared. I have seen this apparent projection of a star on the moon’s face several times, but from the great brilliancy of the star, this was the most beautiful I ever saw. The cause of this phenomenon is involved in impenetrable mystery.’

The following is a representation of the Great Rosse Telescope, along with part of the buildings with which it is connected. In the interior face of the eastern wall a very strong iron arc of about 43 feet radius is firmly fixed, provided with adjustments, whereby its surface facing the telescope may be set very accurately in the plane of the meridian. On this bar, lines are drawn, the interval between any adjoining two of which, corresponds to one minute of time on the Equator. The tube and speculum, including the bed on which the speculum rests, weigh about 15 tons. The telescope rests on an universal joint placed on masonry about 6 feet below the ground, and is elevated or depressed by a chain and windlass; and although it weighs about 15 tons, the instrument is raised by two men with great facility. Of course, it is counterpoised in every direction. The observer when at work, stands in one of four galleries, the three highest of which are drawn out from the western wall, while the fourth or lowest has for its base an elevating platform, along the horizontal surface of which a gallery slides from wall to wall by a machinery within the observer’s reach, but which a child may work. When the telescope is about half an hour east of the meridian, the galleries, hanging over the gap between the walls, present to a spectator below an appearance somewhat dangerous; yet the observer, withcommon prudence, is as safe as on the ground, and each of the galleries can be drawn from the wall to the telescope’s side so readily, that the observer needs no one else to move it for him.

Back to Index Next