There are at present twenty-six submarine cable companies, the combined capital of which is about forty million pounds sterling. Their revenue, including subsidies, amounts to 3,204,060£.; and their reserves and sinking funds to 3,610,000£.; and their dividends are from one to 14¾ per cent. The receipts from the Atlantic cables alone amount to about 800,000£. annually.
The number of cables laid down throughout the world is 1,045, of which 798 belong to governments and 247 to private companies. The total length of those cables is 120,070 nautical miles, of which 107,546 are owned by private telegraph companies, nearly all British; the remainder, or 12,524 miles, are owned by governments.
MAP SHOWING CABLES FROM GREAT BRITAIN TO AMERICA AND THE CONTINENT.The largest telegraphic organization in the world is that of the Eastern Telegraphic Company, with seventy cables, of a total length of 21,859 nautical miles. The second largest is the Eastern Extension, Australasia and China Telegraph Company, with twenty-two cables, of a total length of 12,958 nautical miles. The Eastern Company work all the cables on the way to Bombay, and the Eastern Extension Company from Madras eastward. The cables landing in Japan, however, are owned by a Danish company, the Great Northern. The English station of the Eastern Company is at Porthcurno, Cornwall, and through it pass most of the messages for Spain, Portugal, Egypt, India, China, Japan, and Australia.
MAP SHOWING CABLES FROM GREAT BRITAIN TO AMERICA AND THE CONTINENT.
The third largest cable company is the Anglo-American Telegraph Company, with thirteen cables, of a total length of 10,196 miles.
The British government has one hundred and three cables around our shores, of a total length of 1,489 miles. If we include India and the colonies, the British empire owns altogether two hundred and sixteen cables of a total length of 3,811 miles.
The longest government cable in British waters is that from Sinclair Bay, Wick, to Sandwick Bay, Shetland, of the length of 122 miles, and laid in 1885. The shortest being four cables across the Gloucester and Sharpness Canal, at the latter place, and each less than 300 ft. in length.
Of government cables the greatest number is owned by Norway, with two hundred and thirty-six, averaging, however, less than a mile each in length.
The greatest mileage is owned by the government of France with 3,269 miles, of the total length of fifty-one cables.
The next being British India with 1,714 miles, and eighty-nine cables; and Germany third with 1,570 miles and forty-three cables.
Britain being fourth with ninety miles less. The oldest cable still in use is the one that was first laid, that namely from Dover to Calais. It dates from 1851.
The two next oldest cables in use being those respectively from Ramsgate to Ostend, and St. Petersburg to Cronstadt, and both laid down in 1853.
Several unsuccessful attempts were made to connect England and Ireland by means of a cable between Holyhead and Howth; but communication between the two countries was finally effected in 1853, when a cable was successfully laid between Portpatrick and Donaghadee (31).
As showing one of the dangers to which cables laid in comparatively shallow waters are exposed, we may relate the curious accident that befell the Portpatrick cable in 1873. During a severe storm in that year the Port Glasgow ship Marseilles capsized in the vicinity of Portpatrick, the anchor fell out and caught on to the telegraph cable, which, however, gave way. The ship was afterward captured and towed into Rothesay Bay, in an inverted position, by a Greenock tug, when part of the cable was found entangled about the anchor.
The smallest private companies are the Indo-European Telegraph Company, with two cables in the Crimea, of a total length of fourteen and a half miles; and the River Plate Telegraph Company, with one cable from Montevideo to Buenos Ayres, thirty-two miles long.
The smallest government telegraph organization is that of New Caledonia, with its one solitary cable one mile long.
We will now proceed to give a few particulars regarding the companies having cables from Europe to America.
The most important company is the Anglo-American Telegraph Company, whose history is inseparably connected with that of the trials and struggles of the pioneers of cable laying.
Its history begins in 1851 when Tebets, an American, and Gisborne, an English engineer, formed the Electric Telegraph Company of Newfoundland, and laid down twelve miles of cable between Cape Breton and Nova Scotia. This company was shortly afterward dissolved, and its property transferred to the Telegraphic Company of New York, Newfoundland and London, founded by Cyrus W. Field, and who in 1854 obtained an extension of the monopoly from the government to lay cables.
A cable, eighty-five miles long, was laid between Cape Breton and Newfoundland (22).
Field then came to England and floated an English company, which amalgamated with the American one under the title of the Atlantic Telegraph Company.
The story of the laying of the Atlantic cables of 1857 and 1865, their success and failures, has often been told, so we need not go into any details. It may be noted, however, that communication was first established between Valentia and Newfoundland on August 5. 1858, but the cable ceased to transmit signals on September 1, following.
During that period, ninety-seven messages had been sent from Valentia, and two hundred and sixty-nine from Newfoundland. At the present time, the ten Atlantic cables now convey about ten thousand messages daily between the two continents. The losses attending the laying of the 1865 cable resulted in the financial ruin of the Atlantic company and its amalgamation with the Anglo-American. In 1866 the Great Eastern successfully laid the first cable for the new company, and with the assistance of other vessels succeeded in picking up the broken end of the 1865 cable and completing its connection with Newfoundland.
MAP SHOWING MAIN CABLESMAP SHOWING MAIN CABLES FROM EUROPE AND THEIR CONNECTIONS WITH CANADA AND THE UNITED STATES.Reference to places—A, Heart's Content; B, Placentia; C, St. Peter Miquelon; D, North Sydney, Cape Breton Island; E, Louisbourg; F Canso, Nova Scotia; G, Halifax; H, Bird Rock; I, Madeline Isles; J, Anticosti; K, Charlotte Town, Prince Edward's Island; LLL, Banks of Newfoundland.
The three cables of this company presently in use and connecting Valentia in Ireland with Heart's Content in Newfoundland, were laid in 1873, 1874, and 1880; and (1) are respectively 1886, 1846, and 1890 nautical miles in length. This company also owns the longest cable in the world, that namely from Brest in France to St. Pierre Miquelon, one of a small group of islands off the south coast of Newfoundland and which, strange to say, still belongs to France (6).
The length of this cable is 2,685 nautical miles, or 3,092 statute miles. It was laid in 1869. There are seven cables of a total length of 1773 miles, connecting Heart's Content, Placentia Bay and St. Pierre, with North Sydney, Nova Scotia, and Duxbury, near Boston, belonging to the American company. Communication is maintained with Germany and the rest of the Continent by means of a cable from Valentia to Emden 846 miles long (7); and a cable from Brest to Salcombe, Devon, connects the St. Pierre and Brest cable with the London office of the company (10).1
The station of the Direct United States Cable Company is situated at Ballinskelligs Bay, Ireland (2). Its cable was laid in 1874-5, and is 2,565 miles in length. The terminal point on the other side of the Atlantic is at Halifax, Nova Scotia, from whence the cable is continued to Rye Beach, New Hampshire, a distance of 536 miles, and thence by a land line of 500 miles to New York (17).
The Commercial Cable Company's station in Ireland is at Waterville, a short distance from Ballinskelligs (3). It owns two cables laid in 1885; the northern cable being 2,350, and the southern 2,388 miles long. They terminate in America at Canso, Nova Scotia. From Canso a cable is laid to Rockfort, about thirty miles south of Boston, Mass., a distance of 518 miles (16), and another is laid to New York, 840 miles in length (15). This company has direct communication with the Continent by means of a cable from Waterville to Havre of 510 miles (9), and with England by a cable to Weston-super-Mare, near Bristol, of 328 miles (8).
The Western Union Telegraph Company (the lessees of the lines of the American Telegraph and Cable Company) has two cables from Sennen Cove, Land's End, to Canso, Nova Scotia (4). The cable of 1881 is 2,531 and that of 1882 is 2,576 miles in length. Two cables were laid November, 1889, between Canso and New York (14).
The Compagnie Française du Telegraphe de Paris à New York has a cable from Brest to St. Pierre Miquelon of 2,242 miles in length (5), from thence a cable is laid to Louisbourg, Cape Breton (12), and another to Cape Cod (13). It has also a cable from Brest to Porcella Cove, Cornwall (11).
Those ten cables owned by the six companies named, of the total milage of 22,959, not counting connections, represent the entire direct communication between the continents of Europe and North America.
A new company, not included in the preceding statistics, proposes to lay a cable from Westport, Ireland, to some point in the Straits of Belle Isle on the Labrador coast (Map A32, Map B20).
The station of the Eastern Telegraph Company is at Porthcurno Cove, Penzance, from whence it has two cables to Lisbon, one laid in 1880, 850 miles long, the other laid in 1887, 892 miles long (12), and one cable to Vigo, Spain, laid in 1873, 622 miles long (13). From Lisbon the cable is continued to Gibraltar and the East, whither we need not follow it, our intention being to confine ourselves entirely to a brief account of those cables communicating directly with Europe and America. As already stated, this company has altogether seventy cables, of a total length of nearly 22,000 miles.
The Direct Spanish Telegraph Company has a cable, laid in 1884, from Kennach Cove, Cornwall, to Bilbao, Spain, 486 miles in length (14).
Coming now to shorter cables connecting Britain with the Continent, we have those of the Great Northern Telegraph Company, namely, Peterhead to Ekersund, Norway, 267 miles (15). Newbiggin, near Newcastle, to Arendal, Norway, 424 miles, and thence to Marstrand, Sweden, 98 miles.
Two cables from the same place in England to Denmark (Hirstals and Sondervig) of 420 and 337 miles respectively (17 and 18).
The great Northern Company has altogether twenty-two cables, of a total length of 6,110 miles. The line from Newcastle, is worked direct to Nylstud, in Russia—a distance of 890 miles—by means of a "relay" or "repeater," at Gothenburg. The relay is the apparatus at which the Newcastle current terminates, but in ending there it itself starts a fresh current on to Russia.
The other continental connections belong to the government, and are as follows: two cables to Germany, Lowestoft to Norderney, 232 miles, and to Emden, 226 miles (19 and 20).
Two cables to Holland: Lowestoft to Zandvoort, laid in 1858 (21), and from Benacre, Kessingland, to Zandvoort (22).
Two cables to Belgium: Ramsgate to Ostend (23), and Dover to Furness (24).
Four cables to France: Dover to Calais, laid in 1851 (25), and to Boulogne (26), laid in 1859; Beachy Head to Dieppe (27), and to Havre (28).
There is a cable from the Dorset coast to Alderney and Guernsey, and from the Devon coast to Guernsey, Jersey, and Coutances, France (29 and 30).
A word now as to the instruments used for the transmission of messages. Those for cables are of two kinds, the mirror galvanometer and the siphon recorder, both the product of Sir Wm. Thomson's great inventive genius.
When the Calais-Dover and other short cables were first worked, it was found that the ordinary needle instrument in use on land lines was not sufficiently sensitive to be affected trustworthily by the ordinary current it was possible to send through a cable. Either the current must be increased in strength or the instruments used must be more sensitive. The latter alternative was chosen, and the mirror galvanometer was the result.
The principle on which this instrument works may be briefly described thus: the transmitted current of electricity causes the deflection of a small magnet, to which is attached a mirror about three-eighths of an inch in diameter, a beam of light is reflected from a properly arranged lamp, by the mirror, on to a paper scale. The dots and dashes of the Morse code are indicated by the motions of the spot of light to the right and left respectively of the center of the scale.
The mirror galvanometer is now almost entirely superseded by the siphon recorder. This is a somewhat complicated apparatus, with the details of which we need not trouble our readers. Suffice it for us to explain that a suspended coil is made to communicate its motions, by means of fine silk fibers, to a very fine glass siphon, one end of which dips into an insulated metallic vessel containing ink, while the other extremity rests, when no current is passing, just over the center of a paper ribbon. When the instrument is in use the ink is driven out of the siphon in small drops by means of an electrical arrangement, and the ribbon underneath is at the same time caused to pass underneath its point by means of clockwork.
If a current be now sent through the line, the siphon will move above or below the central line, thus giving a permanent record of the message, which the mirror instrument does not. The waves written by the siphon above the central line corresponding to the dots of the Morse code, and the waves underneath corresponding to the dashes.
The cost of the transmission of a cablegram varies from one shilling per word, the rate to New York and east of the Mississippi, to ten shillings and seven pence per word, the rate to New Zealand. In order to minimize that cost as much as possible, the use of codes, whereby one word is made to do duty for a lengthy phrase, is much resorted to. Of course those code messages form a series of words having no apparent relation to each other, but occasionally queer sentences result from the chance grouping of the code words. Thus a certain tea firm was once astonished to receive from its agent abroad the startling code message—"Unboiled babies detested"!
Suppose we now follow the adventures of a few cablegrams in their travels over the world.
A message to India from London by the cable route requires to be transmitted eight times at the following places: Porthcurno (Cornwall), Lisbon, Gibraltar, Malta, Alexandria, Suez, Aden, Bombay.
A message to Australia has thirteen stoppages; the route taken beyond Bombay being via Madras, Penang, Singapore, Banjoewangie and Port Darwin (North Australia); or from Banjoewangie to Roebuck Bay (Western Australia).
To India by the Indo-European land lines, messages go through Emden, Warsaw, Odessa, Kertch, Tiflis, Teheran, Bushire (Persian Gulf), Jask and Kurrachee, but only stop twice between London and Teheran—namely, at Emden and Odessa. Messages from London to New York are transmitted only twice—at the Irish or Cornwall stations, and at the stations in Canada. Owing to the great competition for the American traffic, the service between London, Liverpool, and Glasgow and New York is said to be much superior to that between any two towns in Britain. The cables are extensively used by stock brokers, and it is a common occurrence for one to send a message and receive a reply within five minutes.
During breakages in cables messages have sometimes to take very circuitous routes. For instance, during the two days, three years ago, that a tremendous storm committed such havoc among the telegraph wires around London, cutting off all communication with the lines connected with the Channel cables at Dover, Lowestoft, etc., it was of common occurrence for London merchants to communicate with Paris through New York. The cablegram leaving London going north to Holyhead and Ireland, across the Atlantic to New York and backviaSt. Pierre to Brest and thence on to Paris, a total distance of about seven thousand miles.
Three years ago, when the great blizzard cut off all communication between New York and Boston, messages were accepted in New York, sent to this country, and thence back to Boston.
Some time ago the cables between Madeira and St. Vincent were out of order, cutting off communication by the direct route to Brazil, and a message to reach Rio Janeiro had to pass through Ireland, Canada, United States, to Galveston, thence to Vera Cruz, Guatemala, Nicaragua, Panama, Ecuador, Peru, Chili; from Valparaiso across the Andes, through the Argentine Republic to Buenos Ayres, and thence by East Coast cables to Rio Janeiro, the message having traversed a distance of about twelve thousand miles and having passed through twenty-four cables and some very long land lines, instead of passing, had it been possible to have sent it by the direct route, over one short land line and six cables, in all under six thousand miles.
Perhaps some of our readers may remember having read in the newspapers of the result of last year's Derby having been sent from Epsom to New York in fifteen seconds, and may be interested to know how it was done. A wire was laid from near the winning post on the race course to the cable company's office in London, and an operator was at the instrument ready to signal the two or three letters previously arranged upon for each horse immediately the winner had passed the post. When the race began, the cable company suspended work on all the lines from London to New York and kept operators at the Irish and Nova Scotian stations ready to transmit the letters representing the winning horse immediately, and without having the message written out in the usual way. When the race was finished, the operator at Epsom at once sent the letters representing the winner, and before he had finished the third letter, the operator in London had started the first one to Ireland. The clerk in Ireland immediately on bearing the first signal from London passed it on to Nova Scotia, from whence it was again passed on to New York. The result being that the name of the winner was actually known in New York before the horses had pulled up after passing the judge. It seems almost incredible that such information could be transmitted such a great distance in fifteen seconds, but when we get behind the scenes and see exactly how it is accomplished, and see how the labor and time of signaling can be economized, we can easily realize the fact.
The humors of telegraphic mistakes have often been described; we will conclude by giving only one example. A St. Louis merchant had gone to New York on business, and while there received a telegram from the family doctor, which ran: "Your wife has had a child, if we can keep her from having another to-night, all will be well." As the little stranger had not been expected, further inquiry was made and elicited the fact that his wife had simply had a "chill"! This important difference having been caused simply by the omission of a single dot.
-.-. .... .. .-.. .-..c h i l l = chill-.-. .... .. .-.. -..c h i l d = child
—Hardwicke's Science-Gossip.
[1]
Cables not fully described in the text, Map B. Eight cables at the Anglo-American Company: 7, Heart's Content to Placentia, two cables; 8, Placentia to St. Pierre; 9, St. Pierre to North Sydney; 10, Placentia to North Sydney, two cables; 11, St. Pierre to Duxbury; 18, Charlotte's Town to Nova Scotia; 19, Government Cable, North Sydney to Bird Rock, Madeline Isles, and Anticosti; 21, Halifax and Bermuda Cable Company's proposed cable to Bermuda.
Cables not fully described in the text, Map B. Eight cables at the Anglo-American Company: 7, Heart's Content to Placentia, two cables; 8, Placentia to St. Pierre; 9, St. Pierre to North Sydney; 10, Placentia to North Sydney, two cables; 11, St. Pierre to Duxbury; 18, Charlotte's Town to Nova Scotia; 19, Government Cable, North Sydney to Bird Rock, Madeline Isles, and Anticosti; 21, Halifax and Bermuda Cable Company's proposed cable to Bermuda.
If an idle pole, C, C, Fig. 12 (P=0.0001 millimeter or 0.13 M), protected all but the point by a thick coating of glass, is brought into the center of the molecular stream in front of the negative pole, A, and the whole of the inside and outside of the tube walls are coated with metal, D, D, and "earthed" so as to carry away the positive electricity as rapidly as possible, then it is seen that the molecules leaving the negative pole and striking upon the idle pole, C, on their journey along the tube carry a negative charge and communicate negative electricity to the idle pole.
FIG. 12.—PRESSURE = 0.0001 MM. = 0.13 M.FIG. 12.—PRESSURE = 0.0001 MM. = 0.13 M.
This tube is of interest, since it is the one in which I was first able to perceive how, in my earlier results, I always obtained a positive charge from an idle pole placed in the direct stream from the negative pole. Having got so far, it was easy to devise a form of apparatus that completely verified the theory, and at the same time threw considerably more light upon the subject. Fig. 13, a, b, c, is such a tube, and in this model I have endeavored to show the electrical state of it at a high vacuum by marking a number of + and - signs. The exhaustion has been carried to 0.0001 millimeter, or 0.13 M, and you see that in the neighborhood of the positive pole, and extending almost to the negative, the tube is strongly electrified with positive electricity, the negative atoms shooting out from the negative pole in a rapidly diminishing cone. If an idle pole is placed in the position shown at Fig. 13, a, the impacts of positive and negative molecules are about equal, and no decided current will pass from it, through the galvanometer, to earth. This is theneutralpoint. But if we imagine the idle pole to be as at Fig. 13, b, then the positively electrified molecules greatly preponderate over the negative molecules, and positive electricity is shown. If the idle pole is now shifted, as shown at Fig. 13, c, the negative molecules preponderate, and the pole will give negative electricity.
FIG. 13 A.—PRESSURE = 0.0001 MM. = 0.13 M.FIG. 13 A.—PRESSURE = 0.0001 MM. = 0.13 MFIG. 13 B.—PRESSURE = 0.0001 MM. = 0.13 M.FIG. 13 B.—PRESSURE = 0.0001 MM. = 0.13 M.FIG. 13 C.—PRESSURE = 0.0001 MM. = 0.13 M.FIG. 13 C.—PRESSURE = 0.0001 MM. = 0.13 M.
As the exhaustion proceeds, the positive charge in the tube increases and the neutral point approaches closer to the negative pole, and at a point just short of non-conduction so greatly does the positive electrification preponderate that it is almost impossible to get negative electricity from the idle pole, unless it actually touches the negative pole. This tube is before you, and I will now proceed to show the change in direction of current by moving the idle pole.
I have not succeeded in getting the "Edison" current incandescent lamps to change in direction at even the highest degree of exhaustion which my pump will produce. The subject requires further investigation, and like other residual phenomena these discrepancies promise a rich harvest of future discoveries to the experimental philosopher, just as the waste products of the chemist have often proved the source of new and valuable bodies.
One of the most characteristic attributes of radiant matter—whence its name—is that it moves in approximately straight lines and in a direction almost normal to the surface of the electrode. If we keep the induction current passing continuously through a vacuum tube in the same direction, we can imagine two ways in which the action proceeds: either the supply of gaseous molecules at the surface of the negative pole must run short and the phenomena come to an end, or the molecules must find some means of getting back. I will show you an experiment which reveals the molecules in the very act of returning. Here is a tube (Fig. 14) exhausted to a pressure of 0.001 millimeter or 1.3 M. In the middle of the tube is a thin glass diaphragm, C, pierced with two holes, D and E. At one part of the tube a concave pole, A', is focused on the upper hole, D, in the diaphragm. Behind the upper hole and in front of the lower one are movable vanes, F and G, capable of rotation by the slightest current of gas through the holes.
FIG. 14—PRESSURE = 0.001 MM. = 1.3 M.FIG. 14—PRESSURE = 0.001 MM. = 1.3 M.
On passing the current with the concave pole negative, the small veins rotate in such a manner as to prove that at this high exhaustion a stream of molecules issues from the lower hole in the diaphragm, while at the same time a stream of freshly charged molecules is forced by the negative pole through the upper hole. The experiment speaks for itself, showing as forcibly as an experiment can show that so far the theory is right.
This view of the ultra-gaseous state of matter is advanced merely as a working hypothesis, which, in the present state of our knowledge, may be regarded as a necessary help to be retained only so long as it proves useful. In experimental research early hypotheses have necessarily to be modified, or adjusted, or perhaps entirely abandoned, in deference to more accurate observations. Dumas said, truly, that hypotheses were like crutches, which we throw away when we are able to walk without them.
In recording my investigations on the subject of radiant matter and the state of gaseous residues in high vacua under electrical strain, I must refer to certain attacks on the views I have propounded. The most important of these questionings are contained in a volume of "Physical Memoirs," selected and translated from foreign sources under the direction of the Physical Society (vol. i., part 2). This volume contains two memoirs, one by Hittorff on the "Conduction of Electricity in Gases," and the other by Puluj on "Radiant Electrode Matter and the So-called Fourth State." Dr. Puluj's paper concerns me most, as the author has set himself vigorously to the task of opposing my conclusions. Apart from my desire to keep controversial matter out of an address of this sort, time would not permit me to discuss the points raised by my critic; I will, therefore, only observe in passing that Dr. Puluj has no authority for linking my theory of a fourth state of matter with the highly transcendental doctrine of four dimensional space.
Reference has already been made to the mistaken supposition that I have pronounced the thickness of the dark space in a highly exhausted tube through which an induction spark is passed to be identical with the natural mean free path of the molecules of gas at that exhaustion. I could quote numerous passages from my writings to show that what I meant and said was the mean free path as amplified and modified by the electrification.2In this view I am supported by Prof. Schuster,3who, in a passage quoted below, distinctly admits that the mean free path of an electrified molecule may differ from that of one in its ordinary state.
The great difference between Puluj and me lies in his statement that4"the matter which fills the dark space consists of mechanical detached particles of the electrodes which are charged with statically negative electricity, and move progressively in a straight direction."
To these mechanically detached particles of the electrodes, "of different sizes, often large lumps,"5Puluj attributes all the phenomena of heat, force and phosphorescence that I from time to time have described in my several papers.
Puluj objects energetically to my definition "Radiant Matter," and then proposes in its stead the misleading term "Radiant Electrode Matter." I say "misleading," for while both his and my definitions equally admit the existence of "Radiant Matter," he drags in the hypothesis that the radiant matter is actually the disintegrated material of the poles.
Puluj declares that the phenomena I have described in high vacua are produced by his irregularly shaped lumps of radiant electrode matter. My contention is that they are produced by radiant matter of the residual molecules of gas.
Were it not that in this case we can turn to experimental evidence, I would not mention the subject to you. On such an occasion as this controversial matter must have no place; therefore I content myself at present by showing a few novel experiments which demonstratively prove my case.
Let me first deal with the radiant electrode hypothesis. Some metals, it is well known, such as silver, gold or platinum, when used for the negative electrode in a vacuum tube, volatilize more or less rapidly, coating any object in their neighborhood with a very even film. On this depends the well known method of electrically preparing small mirrors, etc. Aluminum, however, seems exempt from this volatility. Hence, and for other reasons, it is generally used for electrodes.
If, then, the phenomena in a high vacuum are due to the "electrode matter," the more volatile the metal used, the greater should be the effect.6
FIG. 15.—PRESSURE = 0.00068 MM. = 0.9 M.Here is a tube (Fig. 15, P=0.00068 millimeter, or 0.9 M), with two negative electrodes, AA', so placed as to protect two luminous spots on the phosphorescent glass of the tube. One electrode, A', is of pure silver, a volatile metal; the other, A, is of aluminum, practically non-volatile. A quantity of "electrode matter" will be shot off from the silver pole, and practically none from the aluminum pole; but you see that in each case the phosphorescence, CC', is identical. Had the radiant electrode matter been the active agent, the more intense phosphorescence would proceed from the more volatile pole.
FIG. 16A drawing of another experimental piece of apparatus is shown in Fig. 16. A pear-shaped bulb of German glass has near the small end an inner concave negative pole, A, of pure silver, so mounted that its inverted image is thrown upon the opposite end of the tube. In front of this pole is a screen of mica, C, having a small hole in the center, so that only a narrow pencil of rays from the silver pole can pass through, forming a bright spot, D, at the far end of the bulb. The exhaustion is about the same as in the previous tube, and the current has been allowed to pass continuously for many hours so as to drive off a certain portion of the silver electrode; and upon examination it is found that the silver has all been deposited in the immediate neighborhood of the pole; while the spot, D, at the far end of the tube, that has been continuously glowing with phosphorescent light, is practically free from silver.
The experiment is too lengthy for me to repeat it here, so I shall not attempt it; but I have on the table the results for examination.
FIG. 17The identity of action of silver and aluminum in the first case, and the non-projection of silver in this second instance, are in themselves sufficient to condemn Dr. Puluj's hypotheses, since they prove that phosphorescence is independent of the material of the negative electrode. In front of me is a set of tubes that to my mind puts the matter wholly beyond doubt. The tubes contain no inside electrodes with the residual gaseous molecules; and with them I will proceed to give some of the most striking radiant-matter experiments without any inner metallic poles at all.
In all these tubes the electrodes, which are of silver, are on the outside, the current acting through the body of the glass. The first tube contains gas only slightly rarefied and at the stratification stage. It is simply a closed glass cylinder, with a coat of silver deposited outside at each end, and exhausted to a pressure of 2 millimeters. The outline of the tube is shown in Fig. 17. I pass a current, and, as you see, the stratifications, though faint, are perfectly formed.FIG. 18.—PRESSURE = 0.076 MM. = 100 M.
FIG. 19.—PRESSURE = 0.00068 MM. = 0.9 M.The next tube, seen in outline in Fig. 18, shows the dark space. Like the first it is a closed cylinder of glass, with a central indentation forming a kind of hanging pocket and almost dividing the tube into two compartments. This pocket, silvered on the air side, forms a hollow glass diaphragm that can be connected electrically from the outside, forming the negative pole, A; the two ends of the tube, also outwardly silvered, form the positive poles, B B. I pass the current, and you will see the dark space distinctly visible. The pressure here is 0.076 millimeter, or 100 M. The next stage, dealing with more rarefied matter, is that of phosphorescence. Here is an egg-shaped bulb, shown in Fig 19, containing some pure yttria and a few rough rubies. The positive electrode, B, is on the bottom of the tube under the phosphorescent material; the negative, A, is on the upper part of the tube. See how well the rubies and yttria phosphorescence shows under molecular bombardment, at an internal pressure of 0.00068 millimeter, or 0.9 M.
FIG. 20.—PRESSURE = 0.00068 MM. = 0.9 M.A shadow of an object inside a bulb can also be projected on to the opposite wall of the bulb by means of an outside pole. A mica cross is supported in the middle of the bulb (Fig. 20), and on connecting a small silvered patch, A, on one side of the bulb with the negative pole of the induction coil, and putting the positive pole to another patch of silver, B, at the top, the opposite side of the bulb glows with a phosphorescent light, on which the black shadow of the cross seems sharply cut out. Here the internal pressure is 0.00068 millimeter, or 0.9 M.
FIG. 21.—PRESSURE = 0.001 MM. = 1.3 M.Passing to the next phenomenon, I proceed to show the production of mechanical energy in a tube without internal poles. It is shown in Fig. 21 (P = 0.001 millimeter, or 1.3 M). It contains a light wheel of aluminum, carrying vanes of transparent mica, the poles, A B, being in such a position outside that the molecular focus falls upon the vanes on one side only. The bulb is placed in the lantern and the image is projected on the screen; if I now pass the current, you see the wheels rotate rapidly, reversing in direction as I reverse the current.
Fig. 22.—Pressure = 0.000076 MM. = 0.1 M.Here is an apparatus (Fig. 22) which shows that the residual gaseous molecules when brought to a focus produce heat. It consists of a glass tube with a bulb blown at one end and a small bundle of carbon wool, C, fixed in the center, and exhausted to a pressure of 0.000076 millimeter, or 0.1 M. The negative electrode, A, is formed by coating part of the outside of the bulb with silver, and it is in such a position that the focus of rays falls upon the carbon wool. The positive electrode, B, is an outer coating at the other end of the tube. I pass the current, and those who are close may see the bright sparks of carbon raised to incandescence by the impact of the molecular stream.
You thus have seen that all the old "radiant matter" effects can be produced in tubes containing no metallic electrodes to volatilize. It may be suggested that the sides of the tube in contact with the outside poles become electrodes in this case, and that particles of the glass itself may be torn off and projected across, and so produce the effects. This is a strong argument, which fortunately can be tested by experiment. In the case of this tube (Fig. 23, P = 0.00068 millimeter, or 0.9 M), the bulb is made of lead glass phosphorescing blue under molecular bombardment. Inside the bulb, completely covering the part that would form the negative pole, A, I have placed a substantial coat of yttria, so as to interpose a layer of this earth between the glass and the inside of the tube. The negative and positive poles are silver disks on the outside of the bulb, A being the negative and B the positive poles. If, therefore, particles are torn off and projected across the tube to cause phosphorescence, these particles will not be particles of glass, but of yttria; and the spot of phosphorescent light, C, on the opposite side of the bulb will not be the dull blue of lead glass, but the golden yellow of yttria. You see there is no such indication; the glass phosphoresces with its usual blue glow, and there is no evidence that a single particle of yttria is striking it.Fig. 23.—Pressure = 0.00068 MM. = 0.9 M.
Witnessing these effects I think you will agree I am justified in adhering to my original theory, that the phenomena are caused by the radiant matter of the residual gaseous molecules, and certainly not by the torn-off particles of the negative electrode.
I have already pointed out that the molecular motions rendered visible in a vacuum tube are not the motions of molecules under ordinary conditions, but are compounded of these ordinary or kinetic motions and the extra motion due to the electrical impetus.
Experiments show that in such tubes a few molecules may traverse more than a hundred times themeanfree path, with a correspondingly increased velocity, until they are arrested by collisions. Indeed, the molecular free path may vary in one and the same tube, and at one and the same degree of exhaustion.
Very many bodies, such as ruby, diamond, emerald, alumina, yttria, samaria, and a large class of earthy oxides and sulphides, phosphoresce in vacuum tubes when placed in the path of the stream of electrified molecules proceeding from the negative pole. The composition of the gaseous residue present does not affect phosphorescence; thus, the earth yttria phosphoresces well in the residual vacua of atmospherical air, of oxygen, nitrogen, carbonic anhydride, hydrogen, iodine, sulphur and mercury.
With yttria in a vacuum tube, the point of maximum phosphorescence, as I have already pointed out, lies on the margin of the dark space. The diagram (Fig. 24) shows approximately the degree of phosphorescence in different parts of a tube at an internal pressure of 0.25 millimeter, or 330 M. On the top you see the positive and negative poles, A and B, the latter having the outline of the dark space shown by a dotted line, C. The curve, D E F, shows the relative intensities of the phosphorescence at different distances from the negative pole, and the position inside the dark space at which phosphorescence does not occur. The height of the curve represents the degree of phosphorescence. The most decisive effects of phosphorescence are reached by making the tube so large that the walls are outside the dark space, while the material submitted to experiment is placed just at the edge of the dark space.
FIG. 24—PRESSURE = 0.25 MM. = 330 M.FIG. 24—PRESSURE = 0.25 MM. = 330 M.
Hitherto I have spoken only of the phosphorescence of substances placed under the negative pole. But from numerous experiments I find that bodies will phosphoresce in actual contact with the negative pole.
This is only a temporary phenomenon, and ceases entirely when the exhaustion is pushed to a very high point. The experiment is one scarcely possible to exhibit to an audience, so I must content myself with describing it. A U-tube, shown in Fig. 25, has a flat aluminum pole, in the form of a disk, at each end, both coated with a paint of phosphorescent yttria. As the rarefaction approaches about 0.5 millimeter the surface of the negative pole, A, becomes faintly phosphorescent. On continuing the exhaustion this luminosity rapidly diminishes, not only in intensity but in extent, contracting more and more from the edge of the disk, until ultimately it is visible only as a bright spot in the center. This fact does not prop a recent theory, that as the exhaustion gets higher the discharge leaves the center of the pole and takes place only between the edge and the walls of the tube.
FIG. 25.FIG. 25
If the exhaustion is further pushed, then, at the point where the surface of the negative pole ceases to be luminous, the material on the positive pole, B, commences to phosphoresce, increasing in intensity until the tube refuses to conduct, its greatest brilliancy being just short of this degree of exhaustion. The probable explanation is that the vagrant molecules I introduce in the next experiment, happening to come within the sphere of influence of the positive pole, rush violently to it, and excite phosphorescence in the yttria, while losing their negative charge.
[1]
Presidential address before the Institute of Electrical Engineers, London; continued from SUPPLEMENT, No. 792, page 12656.
Presidential address before the Institute of Electrical Engineers, London; continued from SUPPLEMENT, No. 792, page 12656.
[2]
"The thickness of the dark space surrounding the negative pole is the measure of the mean length of the path of the gaseous molecules between successive collisions. The electrified molecules are projected from the negative pole with enormous velocity, varying, however, with the degree of exhaustion and intensity of the induction current."—Phil. Trans., part i., 1879, par. 530."The extra velocity with which the molecules rebound from the excited negative pole keeps back the more slowly moving molecules which are advancing toward the pole. The conflict occurs at the boundary of the dark space, where the luminous margin bears witness to the energy of the discharge."—Phil. Trans., part i., 1879, par. 507."Here, then, we see the induction spark actually illuminating the lines of molecular pressure caused by the excitement of the negative pole."—R.I. Lecture, Friday, April 4, 1879."The electrically excited negative pole supplies theforce majeure, which entirely, or partially, changes into a rectilinear action the irregular vibration in all directions."—Proc. Roy. Soc., 1880. page 472."It is also probable that the absolute velocity of the molecules is increased so as to make the mean velocity with which they leave the negative pole greater than that of ordinary gaseous molecules."—Phil. Trans., part ii., 1881, par. 719.]
"The thickness of the dark space surrounding the negative pole is the measure of the mean length of the path of the gaseous molecules between successive collisions. The electrified molecules are projected from the negative pole with enormous velocity, varying, however, with the degree of exhaustion and intensity of the induction current."—Phil. Trans., part i., 1879, par. 530.
"The extra velocity with which the molecules rebound from the excited negative pole keeps back the more slowly moving molecules which are advancing toward the pole. The conflict occurs at the boundary of the dark space, where the luminous margin bears witness to the energy of the discharge."—Phil. Trans., part i., 1879, par. 507.
"Here, then, we see the induction spark actually illuminating the lines of molecular pressure caused by the excitement of the negative pole."—R.I. Lecture, Friday, April 4, 1879.
"The electrically excited negative pole supplies theforce majeure, which entirely, or partially, changes into a rectilinear action the irregular vibration in all directions."—Proc. Roy. Soc., 1880. page 472.
"It is also probable that the absolute velocity of the molecules is increased so as to make the mean velocity with which they leave the negative pole greater than that of ordinary gaseous molecules."—Phil. Trans., part ii., 1881, par. 719.]