PHILOSOPHICALTRANSACTIONS.

Munday,July2. 1666.

An Account of aNewkind ofBaroscope, which may be call'dStatical; and of some Advantages and Conveniencies it hath above theMercurial; communicated by Mr.Boyle. The Particular Observations of the PlanetMars, formerly intimated to have been made by Mr.HookinFebruaryandMarchlast. Some Observations, made inItaly, confirming the former; and withall fixing thePeriodof the said Planet's Revolution. Observations, lately made atLondon, of the PlanetJupiter: as also ofSaturn. A Relation of a sad Effect of Thunder and Lightning. An Account of some Books, lately publish'd;videl. The Relations of divers Curious Voyages, by Mons.Thevenot: A Discourse about the Cause of the Inundation of theNile, by Mons.de la Chambre, bothFrench: De Principiis & Ratiocinatione Geometrarum, Contra Fastum Professerum Geometriæ, by Mr.Hobbes: KingSalomonsPourtraiture of Old Age, byJ. Smith, M. D.

* SeeNum. 11. p.185. Phil. Transactions.

As for theNewkind ofBaroscopes, which, not long agoe, * I intimated to you, that my haste would not permit me to give you an account off; since your Letters acquaint me, that you still design a Communicating to theCurious as much Information, as may be, in reference toBaroscopes; I shall venture to send you some Account of what I did but name (in my former Letter) to you.

*The Scales here meant were before competent Eyewitnesses made to turn manifestly with the thousandth part of a grain.

Though by a Passage, you may meet with in the 19th and 20th Pages of myThermometrical Experiments and Thoughts, you may find, that I did some years agoe think upon this New kind of Baroscope; yet the Changes of the Atmosphere's Weight not happening to be then such, as I wish'd, and being unwilling to deprive my self of all other use of the exactest Ballance *, that I (or perhaps any man) ever had, I confess to you, that successive avocations put this attempt for two or three years out of my thoughts; till afterwards returning to a place, where I chanc'd to find two or three pairs of Scales, I had left there, the sight of them brought it into my mind; and though I were then unable to procure exacter, yet my desire to make the Experiment some amends for so long a neglect, put me upon considering, that if I provided aGlass-buble, more than ordinary large and light, even such Ballances, as those, might in some measure perform, what I had tried with the strangely nice ones above-mention'd.

I caused then to be blown at the Flame of a Lamp someGlass-bublesas large, thin and light, as I could then procure, and choosing among them, one, that seem'd the least unfit for my turn, I counterpoised it in a pair of Scales, that would loose theirÆquilibriumwith about the 30th part of a Grain, and were suspended at a Frame. I placed both the Ballance and the Frame by a good Baroscope, from whence I might learn the present weight of the Atmosphere. Then leaving these Instruments together; though the Scales, being no nicer than I have express'd, were not able to shew me all the Variations of the Air's weight that appear'd in theMercurialBaroscope, yet they did what I expected, by shewing me variations no greater, than alter'd the height of Quicksilver half a quarter of an Inch, and perhaps much smaller than those: Nor did I doubt, that, if I had had either tender Scales, or the means of supplying the experiment with convenient accommodations, I should havediscerned far smaller Alterations of the Weight of the Air, since I had the pleasure to see the Buble sometimes in anæquilibriumwith the counterpoise; sometimes, when the Atmosphere was high, preponderate so manifestly, that the Scales being gently stirr'd, the Cock would play altogether on that side, at which the Buble was hung; and at other times (when the Air was heavier) that, which was at the first but the Counterpoise, would preponderate, and, upon the motion or the Ballance, make the Cock vibrate altogether on its side. And this would continue sometimes many daies together, if the Air so long retain'd the same measure of gravity; and then (upon other changes) the Buble would regain anæquilibrium, or a preponderance; so that I had oftentimes the satisfaction, by looking first upon theStaticalBaroscope (as for distinctions sake it may be call'd) to foretell, whether in theMercurialBaroscope the Liquor were high or low. Which Observations though they hold as well in Winter, and several times in Summer (for I was often absent during that season) as the Spring, yet the frequency of their Vicissitudes (which perhaps was but accidental) made them more pleasant in the latter of these seasons.

So that, the matter of Fact having been made out by variety of repeated Observations, and by sometimes comparing severall of those newBaroscopestogether, I shall add some of those Notes about this Instrument, which readily occur to my memory, reserving the rest till another opportunity.

AndFirst, if the ground, on which I went in framing thisBaroscope, be demanded, the answer in short may be; 1. That, though the Glass-buble, and the Glass-counterpoise, at the time of their first being weigh'd, be in the Air, wherein they both are weigh'd, exactly of the same weight; yet they are nothing near of the same bulk; the Buble, by reason of its capacious cavity (which contains nothing but Air, or something that weighs less than Air) being perhaps a hundred or two hundred times (for I have not conveniency to measure them) bigger than the Metalline counterpoise. 2. That according to aHydrostaticalLaw (which you know I have lately had occasion to make out) If two Bodies of equal gravity, but unequal bulk come to be weigh'd in anotherMedium, they will be no longerequiponderant; but if the newMediumbe heavier, the greater Body, as being lighter inSpecie, will loose more of its weight, than the lesser and more compact; but if the newMediumbe lighter than the first, then the bigger Body will outweigh the lesser; And this disparity, arising from the change ofMedium's, will be so much the greater, by how much the greater inequality of bulk there is between the Bodies formerly equiponderant. 3. That, laying these two together, I consider'd, that 'twould be all one, as to the effect to be produced, whether the Bodies were weighed inMediumsof differing gravity, or in the sameMedium, in case its (specifick) gravity were considerably alter'd: And consequently, that since it appear'd by theBaroscope, that the weight of the Air was sometimes heavier, and sometimes lighter, the alterations of it, in point of gravity, from the weight, it was off at first counterpoising of the Buble of it, wouldunequallyaffect so large and hollow a Body, as the Buble, and so small and dense a one, as a Metallin weight: And when the Air by an increase of gravity should become a heavierMedium, than before, it would buoy up the Glass more than the Counterpoise; and if it grew lighter, than it was at first, would suffer the former to preponderate: (The Illustrations and Proof can scarce be added in few words; but, if it be desired, I may, God permitting, send you them at my next leasure:) And though our English Air be about a thousand times lighter, than water, the difference in weight of so little Air, as is but equal in bulk to a Buble, seem'd to give small hopes, that it would be sensible upon a Ballance; yet, by making the Buble very large and light, I supposed and found the Event, I have already related.

Secondly, The hermetically seal'd Glass-buble, I employed, was of the bigness of a somewhat largeOrange, and weigh'd about 1. drachme and 10. grains. But I thought it very possible, if I had been better furnish'd with conveniencies (wherein I afterwards found, I was not mistaken) to make (among many, that might be expected to miscarry) some, that might be preferable to this, either for capacity or lightness, or both; especially if care be taken, that they be not seal'd up, whilst they are too hot. For, though one would think, that it wereadvantagious to rarify and drive out the Air as much as is possible, because in such seal'd Bubles the Air it self (as I have elsewhere shewn) has a weight; yet this advantage countervails not the inconvenience of being obliged to increase the weight of the Glass, which when it includes highly rarified Air, if it be not somewhat strong, will be broken by the pressure of the External Air, as I have sufficiently tryed.

Thirdly, I would have tryed, whether theDrynessandMoistureof the Air would in any measure have alter'd the weight of the Buble, as well as the Variation of Gravity produced in theAtmosphereby other causes; but the extraordinarily constant absence of Fogs, kept me from making Observations of this kind; save that one morning early, being told of a mist, I sent to see (being my self in bed) whether it made the Air so heavy as to buoy up the Buble; but did not learn, that that mist had any sensible operation on it.

Fourthly, By reason of the difficulties and casualties, that may happen about the procuring and preserving such large and light Bubles, as I have been lately mentioning; it may in some cases prove a convenience to be inform'd, That I have sometimes, instead of one sufficiently large Buble, made use of two, that were smaller. And, though a single Buble of competent bignes be much preferable, by reason that a far less quantity and weight of Glass is requisite to comprise an equal capacity, when the Glass is blown into a single Buble, than when it is divided into two; yet I found, that the employing of two instead of one, did not so ill answer my exspectations, but that they may for a need serve the turn instead of the other; than which they are more easier to be procured; And if the Ballance be strong enough to bear so much Glass, without being injur'd: by employing two or a greater number of large Bubles, the effect may be more conspicuous, than if only a single Buble (though a very good one) were employed.

This instrument may be much improved by divers Accommodations, As

First, There may be fitted to theAnsa(or Checks of the Ballance) an Arch (of a Circle) divided into 15. or 20. deg. (more or less, according to the goodness of the Ballance) that the Cock resting over against these Divisions, may readilyand without Calculation shew the quantity of the Angle, by which, when the scales propend either way, the Cock declines from the Perpendicular, and the beam from its Horizontall parallelism.

Secondly, Those, that will be so curious, may, instead of the Ordinary Counterpoise (of Brass) employ one of Gold, or at least of Lead, whereof thelatterbeing of equal weight with Brass, is much less in Bulk, and theformeramounts not to half its bigness.

Thirdly, These parts of the Ballance, that may be made of Copper or Brass, without any prejudice to the exactness, will, by being made of one of those Mettals, be less subject, than Steel, (which yet, if well hardned and polish'd, may last good a great while) to rust with long standing.

Fourthly, Instead of the scales, the Buble may be hung at one end of the Beam, and only a Counterpoise to it at the other, that the Beam may not be burthen'd with unnecessary weight.

Fifthly, The whole instrument, if placed in a small Frame, like a square Lanthorn with Glass-windows, and a hole at the top for the Commerce of the internal and external Air, will be more free from dust, and irregular agitations; to the latter of which, it will otherwise be sometimes incident.

Sixthly, This instrument being accommodated with a light Wheele and an Index (such as have been applyed by the excellent Dr.Chr. Wrento open Weather glasses, and by the ingenious Mr.HooktoBaroscopes) may be made to shew much more minute variations, than otherwise.

Seventhly, And the length of the Beam, and exquisitness of the Ballance, may easily,withoutany of the foregoing helps (and much morewiththem) make the instrument far exacter, than any of those, I was reduced to employ. And to these Accommodations divers others may be suggested by a farther consideration of the nature of the thing, and a longer practice.

Though in some respects thisStaticalBaroscope be inferior to theMercurial; yet in others it has its own advantages and conveniencies above it.

And 1: It confirmsad oculumour former Doctrine, that the falling and rising of theMercurydepends upon the varying weight of the Atmosphere; since in this Baroscope it cannotbe pretended, that aFuga vacui, or aFuniculus, is the cause of the changes, we observe. 2. It shews, that not only the Air has weight, but a more considerable one, than some Learned men, who will allow me to have prov'd, it has some weight, will admit; since even the variation of weight in so small a quantity of Air, as is but equal in bulk to anOrange, is manifestly discoverable upon such Balances, as are none of the nicest. 3. ThisStaticalBaroscope will oftentimes be more parable, than the other: For many will finde it more easie, to procure a good pair of Gold-scales, and a Buble or two, than a long Cane seal'd, a quantity ofQuick-silver, and all the other requisits of theMercurialBaroscope; especially if we comprise the trouble and skill, that is requisite to free the deserted part of the Tube from Air. 4. And whereas the difficulty of removing theMercurialInstrument has kept men from so much as attempting to do it, even to neighbouring places; the Essential parts of theScale-Baroscope (for the Frame is none of them) may very easily in a little room be carried, whither one will, without the hazard of being spoil'd or injur'd. 5. There is not inStaticalBaroscopes, as in the other, a danger of uncertainty, as to the goodness of the Instruments, by reason, that inthesethe Air is, in some more, and in some less perfectly excluded; whereas inthose, that consideration has no place. (And by the way, I have sometimes, upon this account, been able to discover by our new Baroscope, that an esteem'dMercurialone, to which I compared it, was not well freed from Air.) 6. It being, as I formerly intimated, very possible to discoverHydrostatically, both the bigness of the Buble, and the Contents of the cavity, and the weight and dimensions of the Glassie substance (which together with the included Air make up the Buble,) much may be discover'd by this Instrument, as to the Weight of the Air,absoluteorrespective. For, when theQuick-silverin theMercurialBaroscope is either very high, or very low, or at a middle station between its greatest and least height, bringing theScale-Barometer to an exactÆquilibrium(1 with very minute divisions of a Graine,) you may, by watchfully observing, when theMercuryis risen or faln just an inch, or a fourth, of half an inch &c. and putting in the like minute divisions of a Grain to the lighter Scale, till you have again brought the Ballance to anexquisitÆquilibrium; you may, I say, determine, What known weight in theStaticalBaroscope answers such determinate Altitudes of the ascending and descending Quick-silver in theMercurial. And if the Ballance be accommodated with a divided Arch, or a Wheel and Index, these Observations will assist you for the future to determine readily, by seeing the inclination of the Cock or the degree mark'd by the Index, what pollency the Buble hath, by the change of theAtmospheresweight, acquired or lost. Some Observations of this nature I watchfully made, sometimes putting in a 64th.sometimes a 32th.sometimes a 16th.and sometimes heavier parts of a Grain, to the lighter Scale. But one, that knew not, for what uses those little papers were, coming to a window, where my Baroscopes stood, so unluckily shook them out of the Scales, and confounded them, that he robb'd me of the opportunity of making the nice Observations I intended, though I had the satisfaction of seeing, that they were to be made. 7. By thisStaticalInstrument we may be assisted to compare theMercurialBaroscopes ofseveralplaces (though never so distant) and to make some Estimates of the Gravities of the Air therein. As if, for instance, I have found by Observation, that the Buble, I employ, (and one may have divers Bubles of several sizes, that the one may repaire any mischance, that may happen to another) weigh'd just a Drachme, when theMercurialCylinder was at the height of 29½ inches (which in some places I have found amoderatealtitude;) and that the Addition of the 16th part of a gr. is requisite to keep the Buble in anÆquilibrium, when theMercuryis risen an 8th, or any determinate part of an inch above the former station: When I come to another place, where there is aMercurialBarometer, as well freed from Air as mine (for that must be supposed) if taking out myScaleinstrument, it appeare to weigh precisely a Drachme, and theMercuryin the Baroscope there stand at just 29½ inches, we may conclude the Gravity of the Atmosphere not to be sensibly unequal in both those two places, though very distant. And though there be no Baroscope there, yet if there be an additional weight, as for instance, the 16th part of a Grain requisite to be added to the Buble, to bring the scales to anÆquilibrium, it will appear that the Air at this second place is, at that timeso much heavier, than the Air of the former place was, when theMercurystood at 29½ inches.

But in making such comparisons, we must not forget to consider the Situation of the several places, if we mean to make Estimates not only of the weight of the Atmosphere, but of the weight and density of the Air. For, though the Scales wil shew (as has been said) whether there be a difference of weight in the Atmosphere at the two places; yet, if one of them be in a Vale or bottom, and the other on the top or some elevated part of a Hill, it is not to be exspected, that the Atmosphere, in this latter place, should gravitate as much, as the Atmosphere in the former, on which a longer Pillar of Air does lean or weigh.

And the mention, I have made of the differing Situation of Places, puts me in mind of something, that may prove another use of ourStaticalBaroscope, and which I had thoughts of making tryal off, but was Accidentally hindred from the opportunity of doing it. Namely, that by exactly poysing the Buble at the foot of a high Steeple or Hill, and carrying it in its close Frame to the top, one may, by the weight requisite to be added to Counterpoise there to bring the Beam to its Horizontal position, observe the difference of the weight of the Air at the bottom, and at the top; and, in case the Hill be high enough, at some intermediate Stations. But how far this may assist men, to estimate theAbsoluteorComparativeheight of Mountains, and other elevated Places; and what other Uses the Instrument may be put to, when it is duly improved; and the Cautions, that may be requisite in the several cases, that shall be proposed, I must leave to more leasure, and farther Consideration.

To perform, what was promisedNum.11. of these Papers,pag.198; 'tis thought fit now to publish the Particular Observations, concerning the spots inMars, and their motion, as they were made with a 36 foot Telescope, and produced inwriting before theRoyal Society, the 28March1666. by Mr.Hook, as follows;

Having a great desire (saith he) to observe the Body ofMars, whilstAcronycalandRetrograde(having formerly with a Glass of about 12. foot long, observ'd some kind of Spots in the Face of it,) though it be not at present in thePeriheliumof its Orbe, but nearer itsAphelium, yet I found, that the Face of it, when neer its Opposition to the Sun (with a Charge, the 36. foot-glass, I made use off, would well bear) appear'd very near as big, as that of the Moon to thenakedeye; which I found, by comparing it with the Full Moon, near adjoyning to it,March10.

But such had been the ill disposition of the Air for several nights, that from more than 20. Observations of it, which I had made since its beingRetrograde, I could find nothing of satisfaction, though I often imagin'd, I saw Spots, yet theInflective veinsof the Air (if I may so call those parts, which, being interspers'd up and down in it, have a greater or less Refractive power, than the Air next adjoyning, with which they are mixt) did make it so confus'd and glaring, that I could not conclude upon any thing.

On the third ofMarch, though the Air were still bad enough yet I could see now and then the Body ofMarsappearing of the form A: which I presently described by aScheme; and about 10. minutes after, as exactly representing what I saw through the Glass, as I could, I drew theSchemeB. This I was sufficiently satisfied (by very often observing it through the Tube, and changing my Eye into various positions, that so there might be no kind of Fallacy in it) could be nothing else, but some moreDuskyandSpottedparts of the Face of this Planet.

March10. finding the Air very bad, I made use of a very shallow Eye-glass, as finding nothingDistinctwith the greaterCharge; and saw the appearance of it as in C, which I imagin'd, might be the Representation of the former Spots by a lesser charge. About 3 of the Clock the same morning, the Air beingvery bad(though to appearanceexceeding clear, and causing all the Stars to twinckle, and the minute Stars to appear very thick) the body seem'd likeD; which I still suppos'd to bethe Representation of the same Spots through a more confused and glaring Air.

But observingMarch21. I was surprised to find the Air (though not so clear, as to the appearance of small Stars) soexceeding transparent, and the Face ofMarsso very welldefined, and round, and distinct, that I could manifestly see it of the shape in E. about half an hour after Nine at night. TheTriangularspot on the right side (as it was inverted by the Telescope, according to the appearances, through with all the preceedingFiguresare drawn) appear'd very black and distinct, the other towards the left more dim; but both of them sufficiently plain and defin'd. About a quarter before 12. of the Clock the same night, I observ'd it again with the same Glass, and found the appearance exactly, as in F; which I imagin'd to shew me aMotionof the former triangular spot: But designing to observe it again about 3. of the Clock the same Morning, I was hindred by cloudy weather.

ButMarch22. about half an hour after 8. at night, finding the same Spots in the same posture, I concluded, that the preceeding Observation was only the appearance of the same Spots at another height and thickness of the Air: And thought my self confirm'd in this Opinion, by finding them in much the same posture,March23. about half an hour after 9. though the Air was nothing so good as before.

And though I desired to make Observations, about 3. of the Clock those mornings; yet something or other interven'd, that hindred me, tillMarch28. about 3 of the Clock, the Air being light (in weight) though moist and a little hazy; when I plainly saw it, to have the form, represented in I; which is not reconcileable with the other Appearances, unless we allow aTurbinatedmotion ofMarsupon its Center: Which, if such there be, from the Observations madeMarch21. 22. and 23. we may guess it to be once or twice in about 24. hours unless it may have some kind ofLibratingmotion; which seems not so likely. Now, whether certainly so or not, I shall endeavour, as oft as I have opportunity, further to observe.

Sch. I.

A particular direction to theFiguresmentioned in the precedent discourse.

A.March3d.00h.20m.in the morning: the Air having manyinflecting parts dispersed up and down in it; by theWheel Barometer, heavy,

B.Another Scheme, which I drew from my Observation, about 10. minutes after, the same morning. Both these were observed with a very deep Eye-glass.

C.March10d.00h.20m.in the morning: the Air heavy and inflective. Use was made of a shallow or ordinary Charge.

D.March10d.3h.00min the Morning; the Air very heavy and Inflective, which made it glare and radiate, and be more confused, than about 3. hours before. A shallow Charge.

E.March21d.9½h.post merid; the Air light (in weight) and clear, without inflecting parts; the Face appear'd most distinctly of this Forme. A shallow Charge.

F.March21d.11¾h.post merid; the Air continuing very light and clear, without inflecting vapours. A shallow Charge.

G.March22d.8½h.post mer. the Air clear, with few inflecting veins in it, and indifferent light. A shallow Charge.

H.March23d.9½h.post mer. the Air pretty light, but moist, and somewhat thick and hazy, but seem'd to have but few veins, or inflecting parts.

I.March28d.3h.p. m. much the same kind of Air with that of March 23; light, moist, and a little hazy, with some very few veins.

These Observations we shall summarily present the Curious in these parts with, as they were lately presented (by Letter from his Excellency the Ambassadour ofVenice, now residing at the Court ofFrance) to theRoyal Society, in some printed sheets of Paper, entituled,MARTIS, circa Axem proprium Revolubilis, Observationes, BONONIÆ à JO. DOMINICO CASSINO habitæ;come to handJune3. 1666.

In these Papers the ExcellentCassiniaffirms;

1. That with aTelescopeof 24.Palmes, or of about 16Foot, wrought after S.Campani'sway, he began to observeFebruary6. 1666 (st.n.) in the morning, and saw two dark Spots in thefirstFace ofMars.

2. That with the same Glass he observ'dFebr.14/24. in the Evening, in theotherFace of this Planet, two other Spots, like those of the first, but bigger.

3. That afterwards continuing the Observations, he found the Spots of these two Faces to turn by little and little fromEasttoWest, and to return at last to the same situation, wherein he had seen them first.

4. That S.Campani, having also observ'd atRomewith Glasses of 50.Palmesor about 35Foot, likewise of his own contrivance, had seen in the same Planet the samePhenomena.

5.That sometimes he hath seen, during the same night, the two Faces ofMars, one, in the Evening, the other in the Morning.

6. That the Motion of these Spots in the inferior part of the apparent Hemisphere ofMars, is made fromEasttoWest, as that of all the other Celestial Bodies, and is peform'd by Parallels, that declinemuchfrom theEquator, andlittlefrom theEcliptick.

7. That the Spots return the next day to the same situation, 40. minuts later, than the day before; so that in every 36. or 37. daies, about the same hour, they come again to the same place.

8. He promises shortly to give us the particularTablesof this Motion and of its Inequalities, together with theEphemeridesthemselves.

9. He represents, that some otherAstronomershave also made atRomeseveral Observations of these Spots ofMars, fromMarch14/24.toMarch20/30.with Glasses, wrought byEustachio Divini, of 25. and 45. Palmes; Which Spots he makes little differing from his own, of the first Face; as will by and by appear, by the direction to theSchemes.

10. But he adds, that those otherRomanAstronomers, that have observ'd withDivini'sGlasses, will have the Conversion ofMarsto be performed, not in 24 h, 40 m. (as he maintains it is) but in about 13 h.

11. And to evince, that they are mistaken in these Observations of theirs; he alledges, That they assure that the Spots, which they have seen in this Planet, (by anEustachianTelescope) the20/30ofMarch, were small, very distant from oneanother,remote from the middle of the Disk, and theOrientalSpot was less, than theOccidental(as is represented by the Fig. O; like that of the first Face ofMars.) whereas, on the contrary,He (Cassini) pretends to evidence by his Observations, made at the same time atBononia, that, the same day and hour, those Spots were very large, neer one another, in the midst of the Disk, the Oriental bigger than the Occidental (as appears byFig.P, which is that of the second Face ofMars.)

12. Besides, he declares, that thoseAstronomerswere too hasty, in determining, after 5 or 6 Observations only, in how much timeMarsfinish's his Revolution; and denies it to be perform'd in 13 hours: adding, that, though Himself had observ'd for a much longer time, than they; yet he durst not for a great while define, WhetherMarsmade butoneTurn in 24 hours 40 minuts ortwo; and that all, that he could, for a long time affirm, was onely this, that after 24 h. 40 m. this Planet appear'd in the same manner he did before.

13. But since those first Observations, He affirms to have found cause to determine, that the Period of this Conversion is made in the said space of 24 h. 40 m; and not oftner than once within that time; Alledging for proof;

1. That, whereasFebr.6. (st.n.) he saw the Spots of the first Face ofMars, moving from eleven of the Clock in the night, until break of day, they appear'd not afterwards in the Evening after the rising of that Planet (witness several intelligent persons, which he names, that were present at the Observations) Whence he infers, that after 12 hours and 20 minuts, the same Spots did not come about; since that the same, which in the morning were seen in the middle, upon the rising ofMars; after 13 or 14 hours, might have appear'd neer the Occidental Limb. But, because he might be imposed upon by Vapors, whilstMarswas yet so neer theHorizon, he gives this other determination,vid.

2. Whereas he saw the first Face ofMarsthe 6 ofFebruaryat 11 of the clock of the night following; he did not see the same after 18 daies at the same hour; as he ought to have done, if the Period were absolved in the space of 12 h. 20 m.

Sch. II.

3. Again, whereas he sawFebr.24. in the Evening, the other Face ofMars, he could not see the same, the 13. and 15. day ofMarch, to wit after 17 and 19 days; as he should have done, if the Revolution were made in the newly mention'd time.

4. Again, whereas the 27. ofMarchin the Evening he sawthe second Face ofMars, he could not see it the 14. and 16. ofApril.

From all which Observations he Judges it to be evident, that the Period of this Planets Revolution is not perform'd in the space of 12. hours 20, minutes, but in about 24 hours 40 minutes; more exactly to be determin'd by comparing distant Observations: And that those who affirm the former, must have been deceived by not well distinguishing the two Faces, but that having seen the second, taken it for the first.

All which he concludes with this Advertisement, that, when he defines the time of the Revolution ofMars, he does not speak of itsMeanRevolution, but onely of that, which he observ'd, whilstMarswas opposite to the Sun; which is the shortest of all.

The Figures of thePrincipalObservations, represented in the Book here discoursed of, may be seen in the annexedScheme;videl.

K.One of the Faces ofMars, as S.Cassiniobserved itMarch 3. (st.n.) 1666in the Evening, with a Glass of 24 Palmes.

L.The other Face, as he saw itFebr.14/24in the Evening.

M.The first Face, as S.Campanisaw at Rome,March 3. 1666. in the Evening, with a Glass of 50 Palmes.

N.The second Face, as the sameCampaniobserved itMarch18/28. in the Evening.

O.The figure ofMarsas it was seen atRomeby a Telescope ofDiviniof 45 Palmes,March20/30.

P.The Figure of the said Planet, as it was seen the same day and hour at Bononia byCassini; being that of the second Face.

These, as they were made, so they were imparted, by Mr.Hook, as follows:

Sch. III.

A. 1666,June26. between 3. and 4. of the Clock in the morning, I observed the Body ofJupiterthrough a 60 foot-glass, and found the apparent Diameter of it through the Tube, to be somewhat more than 2. degrees, that is, about fourtimes as big, as the Diameter of theMoonappears to thenakedEye. I saw the Limb pretty round, and very well defin'd without radiation. The parts of thePhasisof it had various degrees of Light. Aboutaandf, theNorthandSouthpoles of it (in theFig Q.) 'twas somewhat darker, and by degrees it grew brighter towardsb. ande, two Belts or Zones; the one of which (b) was a small darkBeltcrossing the Body Southward; Adjoyning to which was a smal Line of a somewhat lighter part; and below that again, Southwards, was the great blackBelt c. Between that, ande, the other smaller black Belt, was a pretty large and brightZone; but the middled, was somewhat darker than the edges. I perceiv'd about 3h.15m.near the middle of this, a verydark round Spot, like that represented atg, which was not to be perceiv'd about half an hour before: And I observed it, in about 10. minutes time to be gotten almost tod, keeping equal distance from theSatelles h, which moved also Westwardly, and was joyn'd to the Disk ati, at 3h.25m.After which, the Air growing very hazy, and (as appeared by theBaroscope) very light also (in weight) I could not observe it: So that it was sufficiently evident, that this black Spot was nothing else, save the shadow of theSatelles h, Eclipsing a part of the Face of Jupiter. About two hours before, I had observed a large darker spot in the biggerBeltaboutk, which in about an hour or little more (for I did not exactly observe the time, nor draw theFigureof it) moving Westwards, disappear'd. About a week before, I discover'd also, together with a Spot in theBelt c, another Spot in theBelt e, which kept the same way and velocity with that of theBelt c. The other threeSatellitesin the time of this Eclipse, made by theSatelles, were Westwards of the Body ofJupiter; appearing as bright through the Tube, as the Body ofJupiterdid to the naked Eye, and I was able to see them longer through the Tube, after the day-light came on, than I was able to see the Body ofJupiterwith my naked eye.

Sch. IV.

June29 1666. between 11. and 12. at night I observed the Body ofSaturnthrough a 60. foot Telescope, and found itexactly of the shape represented in theFigureR. TheRingappear'd of a somewhat brighter Light than theBody; and the black linesa a, crossing the Ring, andb bcrossing the Body (whether Shadows or not, I dispute not) were plainly visible: whence I could manifestly see, that theSouther-most part of the Ring was onthisside of the Body, and theNorthernpart, behind, or covered by the Body.

This Relation was written by that worthy Gentleman,Thomas NealeEsquire, (the thenHigh Sheriffof the County ofHampshire, when this disaster hapned) to a Friend of his inLondon, as follows;

On the 24 ofJanuary1665/6, one Mr.BrooksofHampshire, going fromWinchestertowards his house nearAndoverin very bad Weather, was himself slain by Lightning, and the Horse, he rode on, under him. For about a mile fromWinchesterhe was found with his Face beaten into the ground, one leg in the stirrup, the other in the Horses mane; his Cloaths all burnt off his back, not a piece as big as a handkerchief left intire, and his hair and all his body singed. With the force, that struck him down, his nose was beaten into his face, and his Chin into his Breast; where was a wound cut almost as low, as to his Navil; and his cloaths being, as aforesaid, torn, the pieces were so scatter'd and consum'd, that not enough to fill the crown of a hat could be found. His gloves were whole, but his hands in them sing'd to the bone. The hip-bone and shoulder of his Horse burn't and bruised; and his saddle torn in little pieces. This was what appear'd to the Coroners inquest, and so is likely to be as near truth, as any is to be had.

So far this Letter: Which, if it had come soon enough to the hands of thePublisher, would have been joyned to a likeRelation, inserted in the next foregoing Papers (Num.13.) of an accident hapn'd at a later time. With both which may be compared the Account, formerly published in Latin by the Learned Dr.Charleton, concerning the Boy, that wasThunder-struck nearNantwich in Cheshire;the Title of the Book beingAnatome Pueride Cælo tacti: such Relations, when truly made, well deserving to be carefully recorded for farther consideration.

RELATIONS OF DIVERS CURIOUS VOYAGES, byMons. Thevenot, the thirdTome, inFrench. This Book contains chiefly, the Ambassie of theDutchintoChina, translated out of the Dutch manuscript: A Geographical description ofChina, translated out of a Chinese Author byMartinius: And the Account, which the Directors of the Dutch East-India Company made to the States General, touching the state of affairs in the East-Indies, when their late Fleet parted from thence. To touch some things of aGeographicalandPhilosophicalnature, contained therein, we shall take notice;

1. How the Kingdom ofChinais peopled; there being according to the best computation (which is there made with singular care) above 58 millions of Men, not counting Magistrates, Soldiers, Priests, Eunuchs, Women and Children; so that it may not be altogether strange, if one should affirm, there were 200 millions of people, of all sorts, in that Kingdom.

2. ThatCatayis nothing else, but theSixNorthern Provinces ofChina, separated from the otherNine, by the great RiverKIANG; and that the CityCambaluis the same with that ofPeking; theTartars, who carry every three years their Tribute to the Emperor ofChina, constantly calling the said Provinces and City by those names ofCatay, andCambalu.

3. ThatChinais so well furnisht with Rivers, and cut Channels, that men may go from the most Southern to the most Northern part thereof by water, except one daies journey; as the Dutch Ambassadours did, embarking atCanton, which is 23d. 48m. Northern Latitude, and landing atPeking, which is about 40d; having only travell'd one daies journey over some Mountains of the ProvinceKiamsi.

4. That the people ofChinaare exceeding industriousHusbandmen making, among other waies of improving their soile, great use of Flouding.

5. That thePhysiciansofChinado cure Sicknesses with much ease, and in a short time: That they have very ancient Books of the nature and vertues of Herbs, Trees and Stones: That their Modern Physicians (as well as their Ancient ones did) write of the Prognosticks, Causes, Effects, &c. of Diseases. That their Remedies consist for the most part ofSimplesandDecoctions,Cauteries,Frictions; without the use ofBloud letting:That they have such an excellent skill and method in feeling thePulse, that by the means thereof they discover even the most latent causes of Diseases; taking a good half hour, when they visit a Patient, in feeling and examining his Pulse: That they prescribe much the use ofThe; and the drinking alwayes warme, whatever they drink: To the custome of both which it's imputed, that the inhabitants ofChinado spit very little, nor are subject to the Stone or Gout: That they prise highly the RootGinseng, as an extraordinary Restorative and Cordiall, recovering frequently with it agonizing persons; one pound of it being paid with 3 pounds of silver. As for theirChymists, (of which they have also good store) they go beyond ours, promising not only to make Gold, but to give Immortality.

6. That theirNobilityis raised from Learning and Knowledge, without regard to Bloud or Parentage, excepting the Royall Family.

7. That inCHEKIAN, a maritime Province, whence is the shortest cut ofChinatoJapan, is the best and plentifullestSilk-tradein the world: And that there every year the Mulberries are cutt, and kept down, that they grow not into Trees for the easier gathering of the Leaves, there being adoubleSilk-harvest in that Country, as there is in severall other parts of the East-indies; (both which there is hope, will shortly be imitated inVirginia.)

8. That the way of makingPorcelaneis this: (Which is the rather inserted here, because it agrees so well with an Account, we received a while since from a very Curious and intelligent Person of Amsterdam.) There is in the Province ofNankina Town, call'dGoesifolswhence they draw the Earth forPorcelaine, which is found between the Rocks of Mountains. This Earth they beat very small, and stamp it to a very fine Powder, and then put it into Tubs fill'd with water; where the finest part sinks to the bottom. Afterwards 'tis kneaded in the form of small Cubes, of the weight of about 3.Catti(aCattibeing 20 Ounces.) These pieces thus wrought are sold to the people, that commonly in great numbers fetch them, coming from the TownSintesimo(otherwiseJontiou) in the Province ofKiansy, being about 50 miles distant fromWotsing, neer the CityKIANSY; which people transport them to their homes, and there bake them in this manner: They heat their Ovens well, for the space of 15 daies successively, and then keep them so close, that no Air may get in; and after 15otherdaies are pass'd, they open the Oven in the presence of an Officer, who takes every fifth vessel of each fashion for the service of the Emperor: Which done, the rest is sold to those ofUcienien, whence it is transported all over the Country. So that the Earth is not prepared, inNankin, where 'tis found, because the people of that Province have not the skill of working it, as the other above-mention'd; who also alone have the Art of coloring it, which they keep as a great Secret, not teaching it to any, but their Children and next Kindred.

9. ThatMuskis nothing else, but the Testicles of a Beast like a Dear, found in the Province ofHonan; and that, when tis good and unmixt, as it comes from the Animal, they sell it even inNankinandPekin, for 30. or 35.Teyls(that is, about so many Crowns) theCatti.

Many other curious informations might be borrow'd from this Author, concerning the Customs, Studies, Exercises of theChinese; of the number of the people of each Province; of the Natural productions of the Earth and Rivers there; of the Structure and Antiquity of their Wall; of the Magnificence of their Porcelain Tower &c.; but, remitting for these things to the Book it self, we shal only add a piece of Oeconomy, used by theHolland-Merchants in their Commerce withChina, which is, that they dry abundance of Sage-leaves, role them up, andprepare them likeThe, and carrying it toChina, as a rare drogue, get for one pound of it, fourtimes as muchThe.

A DISCOURSE ABOUT THE CAUSES OF THE INUNDATION OF THE NILE, inFrench. The Author of this Book is Monseiurdela Chambre, who being perswaded from several Circumstances, that accompany the Overflowing of this River, that it cannot proceed from Rain, ventures to assign for a Cause ofit, and of all the other effects that happen at the time of its swelling, theNiter, wherewith that water abounds.

The discourse having six parts, the Author endeavours to shew in the

First, that the Waters of theNileare Nitrous, explicating the Nature of Salt, and Saltpeter, and imputing the fertility of the Earth, as well us the fecundity of Animals, to Salt. Where he shews, that all things, that serve to improve Land, are full of Salt; and that 'tis observ'd, that grain steep'd in Vrine, before sowing, rises sooner, and becomes fuller and stronger, than else. Adding, that that, which renders the Seed of Animals prolifick, is, that one of theSpermatickveins hath its Origine from theEmulgent, through which the Nitrous and Saline Serosities, that discharge themselves into the Kidneys and Bladder, do pass.

In theSecond, he examins, what is Fermentation, and how 'tis perform'd; affirming, that, what thrusts forth Plants in the Spring, is, that the Earth being fermented by theNiter, it harbours, the Nitrous spirits insinuate themselves into their Pores.

In theThirdhe treats of all the Circumstances, observable in the Inundation of the Nile. 'Tis affirm'd, that 3 or 4 days before that River begins to overflow, all its water is troubled: that then there falls a certain Dew, which hath a fermenting vertue, and leavens a Paste exposed to the Air: that the Mud, which has been drawn out of the water, grows heavier, when the overflowing begins, then it was before, and that by the increase of the weight of that Mud, they judge of the greatness of the approaching inundation. The Author pretends, thatthe Niter, which theNileis stored with, is the cause of all these strange effects, and of many others, by him alledged. For,saith he, when the Nitre is heated by the heat of the Sun, it ferments, and mingling with the water, troubles it, and swells it, and makes it pass beyond its banks; after the same manner, as the Spirits in new Wine render it troubled, and make it boyle in the vessel. And it seems not likely to him, that the Mud, found in theNile, should come a far off; for then it would at last so raise the banks of this River, that it would not be able to overflow them any longer. Whereas 'tis more than 2000 years, that the banks thereof are not grown higher, there being now requisite but 16. cubits for overflowing the Land, no more than there was in the time ofHerodotus. Which shews,saith he, that this Mud is nothing but a volatilNiter, which exhaling, doth not increase the Earth. As for theÆgyptianDew, and the increase of the weight of the Mud, he adscribes them to the same Cause. For the spirits of Nitre abounding in theNile, when raised into the Air with the vapors, that exhale continually from this River, there is made out of their mixture, a Dew, that refreshes the Air, makes sickness to cease, and produces all those admirable effects, that make theÆgyptianswish for it so passionately. And the same spirits of Niter, being joyned to the Paste, and to the Mud, raise the one, and augment the weight of the other. That, which Mr.Buratiniobserves, that at the time of this inundation, the Niter-pits of the neighboring places vomit out liquid Niter, and that one may see issue out of the Earth abundance of Chrystals of Nitre, is alledged to fortify this conjecture; Which is yet more confirm'd by the Fertility, communicated to the Earth by the Mud of this River. For, plants do grow there in such abundance, that they would choak one another, if it were not remedied by throwing Sand upon the Fields; insomuch that theÆgyptiansmust take as much pains to spread Sand to lessen the fatness of their Land, as other Nations do, to spread dung or other manure upon theirs to increase the fatness.

In theFourthandFifth, the Author undertakes to prove, that all those strange effects cannot be attributed to Rain or Snow,and that the overflowing of theNilealways happens at a certain day.

In theLast, he alledges some Relations, serving to confirm his Opinion; Which are too long here to insist upon.

DE PRINCIPIIS ET RATIOCINATIONE GEOMETRARUM, Contra Fastum Professorum Geometriæ;AuthoreThoma Hobbes. It seems, that this Author is angry with all Geometricians, but himself; yea he plainly saith in the dedication of his Book, thathe invades the whole Nation of them; and unwilling, it seems, to be call'd to an account for doing so; He will acknowledge no judge ofthisAge; but is full of hopes, that posterity will pronounce for him. Mean while he ventures to advance thisDilemma;Eorum qui de iisdem rebus mecum aliquid ediderunt, aut solus insanio Ego, aut solus non insanio; tertium enim non est, nisi (quod dicet forte aliquis) insaniamus omnes.Doubtless, one of these will be granted him.

As to the Book it self, he professes, that he doth not write it againstGeometry, butGeometers; and that his design in it is, to shew, That there is no less uncertainty and falsity in the writings ofMathematicians, than there is in those ofNaturalists,Moralists, &c., though he judges, thatPhysicks,Ethicks,Politicks, if they were well demonstrated, would be as certain as theMathematicks.

Attacking the Mathematical Principles as they are found in Books, and withall some Demonstrations, he takes to taskEuclidhimself, instead of all, as the Master of all Geometricians, and with him his best interpreter,Clavius, examining in theFirstplace, thePrinciplesofEuclid:Secondly, Declaring false, what is superstructed upon them, whether byEuclid, orClavius, or anyGeometerwhatsoever that hath made use of those or other (as he is pleased to entitle them)falsePrinciples.Thirdly, Pretending, that he means so to combat all, both Principles and Demonstrations, undertaken by him, as that he will substitute better in their room, least he should seem to undermine the Science it selfe.

The particulars, which he undertakes to reform, are,

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