[Sidenote: * _Those _Five_ Suns, that appear'd the 29 _March_, A. 1629. at
_Rome_, between 2 or 3 of the Clock, in the afternoon, were thus posited;
that the two of them, which were in the intersection of two Circles,
appear'd in that of a Circle, which passed through the Sun's Diske, with
another, that was _Concentrick_ to the Sun: as may be seen in _Figure III_.
borrow'd (for the easier comparing them together) out of _Des-Cartes_ his
_Meteors_, cap. X._]
This Appearance is look't upon as one of the notablest, that can be seen,
by reason of the _Excentricity_ of the Circle H D N, and because that the
_Parhelia_ * were not in the Intersection of the Circle D E B O with the
great Circle S C H N, but in that of the Semi-circle H D N.
As for the two odd _Rainbows_; they appear'd at _Chartres_ the 10. of
_August_, 1665. about half an hour past six in the Evening; and did cross
one another almost at right Angles, as may be seen by _Fig._ IV.
[Illustration]
The Rainbow, which was opposite to the Sun, in the usual manner, was more
deeply colour'd, than that, which cross'd it; though even the Colours of
the first _Iris_ were not so strong, as they are now and then seen at other
times.
The greatest height of the stronger Rainbow, was about 45. degrees; the
feebler Rainbow lost one of its Legs, by growing fainter, about 20 degrees
above the stronger; and the Leg below appear'd continued to the _Horizon_.
These Rainbows did not _Just_ decussate one another at right Angles; there
was some 6 or 7 degrees difference. The fainter, seem'd to be a Portion of
a great Circle; and the stronger was but a Portion of a small Circle, as
usually.
The Sun, at their appearance, was about 6 degrees high above the _Horizon_,
and towards the 17 _Azimuth_ of the West, Northward.
{222}
The Observer, M. _Estienne_, notes, that, when he made this Observation,
the River of _Chartres_, which runs very near from _South_ to _North_, was
betwixt him and the Rainbow; and that he stood Level with this River,
whence he was distant not above 150 paces: which he adds, that the Curious
may the better judge of this Observation.
* * * * *
_A Relation of an Accident by Thunder and Lightning, at _Oxford_._
This was imparted by Dr. _Wallis_ in a Letter, written at _Oxford_, May 12,
1666. to the _Publisher_, as follows:
I should scarce have given you so soon the trouble of another Letter, were
it not for an Accident which hapn'd here _May_ 10. I had that afternoon,
about 4 of the clock heard it thunder at some distance. About 5 of the
clock the Thunder coming nearer to us; it began to rain, and soon after
(the rain withal increasing) the Thunder grew very loud, and frequent, and
with long ratling Claps (though not altogether so great, as I have some
other times heard:) and the Lightning with flashes very bright
(notwithstanding the clear day-light) and very frequent, (when at the
fastest, scarce a full minute between one flash and another; many times not
so much, but a second flash before the Thunder of the former was heard:)
The Thunder for the most part began to be heard about 8 or 10 second
minutes after the flash; as I observ'd for a great part of the time by my
Minute-Watch: but once or twice I observ'd it to follow (in a manner)
immediately upon it, as it were in the same moment; and the lightning
extream red and fiery. I do not use to be much apprehensive of Thunder and
Lightning, but I was at this time (I know not well, why?) very
apprehensive, more than ordinary, of mischief to be done by it, for it
seem'd to me to be very low and near us (which made me so particular, as to
observe the distance of the flash by the noise) and very frequent, and
bright, so that, had it been by night as it was by day, it would have been
very terrible. And, though I kept within doors, yet I sensibly discover'd a
stinking sulphureous smell in the Air. About 7 of the clock it ended,
before which time I had news brought me of a Sad Accident upon the {223}
water at _Medley_ about a Mile or somewhat more distant from hence. Two
Schollars of _Wadham_-Colledge, being alone in a Boat (without a Water-man)
having newly thrust off from shore, at _Medley_, to come homewards,
standing near the Head of the Boat, were presently with a stroke of Thunder
or Lightning, both struck off out of the Boat into the Water, the one of
them stark dead, in whom, though presently taken out of the Water (having
been by relation, scarce a minute in it) there was not discerned any
appearance of life, sense, or motion: the other was stuck fast in the Mud
(with his Feet downwards, and his upper parts above water) like a post not
able to help himself out; but, besides a present stonying or numness, had
no other hurt; but was for the present so disturb'd in his senses, as that
he knew not, how he came there out of the Boat, nor could remember either
Thunder or Lightning, that did effect it: and was very feeble and faint
upon it; which (though presently put into a warm Bed) he had not thoroughly
recover'd by the next Night; and whether since he have or no, I know not.
Others in another Boat, about 10 or 20 yards from these (as by their
description I estimate) felt a disturbance and shaking in their Boat, and
one of them had his Chair struck from under him, and thrown upon him; but
had no hurt. Those immediately made up to the others, and (some leaping
into the Water to them) presently drew them either into the Boat or on
Shore; yet none of them saw these two fall into the Water (not looking that
way) but heard one of them cry out for help presently upon the stroke, and
smelt a strange stinking smell in the Air; which, when I asked him, that
told it me, what kind of stink? he said, like such a smell, as is perceived
upon the stricking of Flints together.
He that was dead (when by putting into a warm Bed, and rubbing, and putting
strong waters into his Mouth, &c. no life could be brought into him) was
the next morning brought to town; where, among the multitudes of others,
who came to see, Dr. _Willis_, Dr. _Mellington_, Dr. _Lower_, and my self,
with some others, went to view the Corps: where we found no wound at all in
the skin, the face and neck swart and black, but not more, than might be
ordinary, by the settling of the blood: On the right side of the neck was a
little blackish spot about an inch long, and {224} about a quarter of an
inch broad at the broadest, and was, as if it had been sear'd with a hot
iron; and, as I remember, one somewhat bigger on the left side of the neck,
below the Ear. Streight down the breast, but towards the left side of it,
was a large place about three quarters of a Foot in length, and about two
inches in breadth, in some places more, in some less, which was burnt and
hard, like Leather burnt with the fire, of a deep blackish red Colour, not
much unlike the scorch'd skin of a rosted Pig. And on the fore-part of the
left Shoulder such another spot about as big as a Shilling; but that in the
neck was blacker and seem'd more sear'd. From the top of the right
shoulder, sloping downwards towards that place in his Breast, was a narrow
Line of the like scorched skin; as if somewhat had come in there at the
neck, and had run down to the breast, and there spread broader.
The buttons of his _Doublet_ were most of them off; which, some thought
might have been torn off with the blast, getting in at the neck, and then
bursting its way out: for which the greatest presumption was (to me) that,
besides 4 or 5 buttons wanting towards the bottom of the Breast, there were
about half a dozen together clear off from the bottom of the collar
downwards, and I do not remember, that the rest of the buttons seem to be
near worn out, but almost new. The collar of his doublet just over the
fore-part of the left shoulder was quit broken asunder, cloth and
stiffening, streight downwards, as if cut or chop'd asunder, but with a
_Blunt_ tool; only the inward linnen or fustian lineing of it was whole, by
which, and by the view of the ragged Edges, it seem'd manifest to me, that
it was by the stroak inward (from without) not outwards from within.
His _Hat_ was strangely torn, not just on the Crown, but on the side of the
hat, and on the brim. On the side of it was a great hole, more than to put
in ones fist through it: some part of it being quite struck away, and from
thence divers gashes every way, as if torn, or cut with a _Dull_ tool, and
some of them of a good length, almost quite to the edges of the brim. And,
beside these, one or two gashes more, which did not communicate with the
hole in the side. This also I judged by a stroke inwards; not so much from
the view of the edges of those gashes (from which there was scarce any
judgement to be made either way) but {225} because the lining was not torn,
only ript off from the edge of the hat (where it was sow'd on) on that
side, where the hole was made. But his hat not being found upon his head,
but at some distance from him, it did not appear, against what part of the
head that hole was made.
Upon the rest of his Cloaths, I do not know of any further effect, nor did
we smell any sulphurous scent about them: which might be, _Partly_ because
it was now a good while after the time, and _Partly_ by reason of their
being presently drenched in the water into which he fell.
The night following, the three _Doctors_ above mentioned, and my self, with
some Chirurgions (besides a multitude of others) were present at the
opening of the head, to see if any thing could be there discover'd; but
there appear'd no sign of contusion; the brain full and in good order; the
nerves whole and sound, the vessels of the brain pretty full of Blood. But
nothing was by any of them discern'd to be at all amiss. But it was by
candle-light, and they had not time to make very nice Observations of it
(the Body being to be buried by and by) and the croud of People was a
further hindrance. But if any thing had been considerably out of order to
the view, it would surely have been by some of them discover'd. Some of
them thought, they discern'd a small fissure or crack in the skull; and
some who held it, while it was sawing off, said, they felt it Jarring in
their hands, and there seem'd to the eye something like it, but it was so
small, as that by candle-light we could not agree it certainly so to be.
Some of the _Hair_ on the right Temple was manifestly singed, or burnt; and
the lower part of that Ear blacker, than the parts about it, but soft; and
it might be only the settling of the Blood. The upper part of the left
shoulder, and that side of the neck, were also somewhat blacker than the
rest of the Body, but whether it were by the blow, which broke the collar,
and scorch'd the round red spot thereupon, or only by settling of the
Blood, I cannot say; yet I think, it might very well be, that both on the
head, and on this side of the neck, there might be a very great blow, and a
contusion upon it (and seems to have been so, by the tearing of the hat,
and breaking the collar, if not also cracking of the skull) and yet no sign
of such contusion, because dying so immediately, there was not time for the
Blood to gather {226} to the part and stagnate there (which in bruises is
the cause of blackness) and it was but as if such a blow had been given on
a Body newly dead; which does not use to cause such a symptom of a bruise,
after the Blood ceases to circulate.
Having done with, the Head, they open'd the _Breast_, and found that
burning to reach quite through the skin, which was in those scorch'd places
hard and horney, and shrunk up, so as it was not so thick as the soft skin
about it: but no appearance of any thing deeper than the skin; the Muscles
not at all disorder'd or discolour'd (perhaps, upon the reason, that was
but now said of the Head, Neck and Shoulder). Having then taken off the
_Sternum_, the Lungs and Heart appear'd all well, and well-colour'd without
any disorder.
This is the sum of what was observ'd; only that the whole Body was, by
night, very much swell'd, more than in the morning; and smelt very strong
and offensively: Which might be by the hotness of the weather, and by the
heat of the place occasion'd by the multitude of People.
* * * * *
_An Experiment to examine, what _Figure_, and _Celerity_ of _Motion_
begetteth, or encreaseth _Light_ and _Flame_._
This was communicated by Dr. _Beale_, as follows;
_May_ 5. 1665. fresh Mackrels were boyl'd in Water, with salt and sweet
herbs; and, when the Water was perfectly cold, the next morning, the
Mackrels were left in the Water for pickle.
_May_ 6. more fresh Mackrels were boyl'd in like Water; and _May_ 7. both
Water and Mackrels were put into the former Water, together with the former
Mackrels. (Which circumstances I do particularize, because, whether, the
mixture of the pickle of several ages, and a certain space of time, or
whatever else was necessary, and wanting, the trial did not succeed with
like effect at other times).
But now on the next _Munday_ (_May_ 8). evening, the Cook stirring the
Water, to take out some of the Mackrels, found the Water at the first
motion become very luminous, and the Fish shining through the Water, as
adding much to the Light, which the water yielded. The water by the mixture
of Salt and Herbs, {227} in the boyling, was of it self thick and rather
blackish, than of any other clear colour: yet being stirr'd, it shin'd, and
all the fish appear'd, more brightly luminous in their own shapes.
Wherever the drops of this water (after it was stirr'd) fell on the Ground,
or Benches, they shin'd: And the Children took drops in their hands, as
broad as a penny, running with them about the house, and each drop, both
near and at distance, seem'd by their shining as broad as a six pence, or a
shilling, or broader.
The Cook turn'd up the side of the Fish, which was lowest, and thence came
no shining: and after the water was for some good time settled, and fully
at rest, it did not shine at all.
On _Tuesday_ night (_May_ 9). we repeated the same Trial, and found the
same effects. The water, till it was stirr'd, gave no light, but was thick
and dark, as we saw by day-light, and by candle-light. As soon as the
Cook's hand was thrust into the water, it began to have a glimmering; but
being gently stirr'd by the hand moving round (as the Dairy-maid do to
gather the Curds for Cheese) it did so shine, that they, who look'd on it
at some distance, from the farther end of another room, thought verily, it
was the shining of the Moon through a Window upon a Vessel of Milk; and by
brisker Circulation it seem'd to flame.
The Fish did then shine as well from the Inside, as the Outside, and
chiefly from the Throat, and such places, as seem'd a little broken in the
boyling.
I took a piece that shin'd most, and fitted it as well as I could devise in
the night, both to my great _Microscope_, and afterwards to my little one;
but I could discern no light by any of these Glasses; nor from any drops of
the shining water, when put into the Glasses. And _May_ 10. in the
brightest rayes of the Sun, I examin'd, in my great _Microscope_, a small
broken piece of the Fish, which shin'd most the night before. We could find
nothing on the surface of the Fish very remarkable. It seem'd whitish, and
in a manner dried, with deep inequalities. And others, as well as my self,
thought, we saw a stream, rather darkish, than luminous, arising like a
very small dust from the Fish: And rarely here and there, a very small; and
almost imperceptible sparkle in the Fish. Yet of these _sparkles_ we are
_certain_; we numbered them, and agreed in the number, order and place. Of
the _steam_ I am not confident, but do suspect our Eyes in the {228} bright
Sun, or that it might be some dust in the Aire.
The great _Microscope_ being fitted in the day-light for this piece of
Fish, we examin'd it that night, and it yielded no light at all, either by
the view of the Glass, or otherwise.
Finding it dry, I thought that the moisture of Spittle, and touching of it,
might cause it to shine: and so it did, though but a very little, in a few
small sparks, which soon extinguish'd. This we saw with the bare eye; not
in the Glass.
The Fish were not yet fetide, nor insipid to the best discerning palats:
And I caused two Fish to be kept for further Tryal, two or three days
longer, till they were fetide in very hot weather; and then I expected more
brightness, but could find none, either in the water, by stirring it, or in
the Fish, taken out of the water.
And some Trials I made afterwards with other boyl'd Mackrels (as is above
said) with like pickle, but failed of the like success.
This season serves for many Trials in this kind, and by better
_Microscopes_, or better ordered. And in these Vulgarities we may perhaps
as well trace out the cause and nature of Light, as in Jewels of greatest
value, &c.
* * * * *
_Some Considerations touching a Letter in the _Journal des Scavans_ of _May
24. 1666_._
In _Num._ 9. of these _Transactions_ were publish'd the _Schemes_ and
_Descriptions_ of certain Ways of _Sounding the Depth of the Sea without a
Line_; and of _Fetching up Water from the bottom of it_; together with some
Experiments already made with the former of these two Contrivances. The
Author of the French _Journal des Scavans_ found good, to insert them both
in his _Journal_ of _May_ 3. but in another of _May_ 24. intimates, that
the said _Schemes_ and their _Descriptions_ are not very clear and
intelligible (he means, that they were not well understood by _French_
Readers) proposing also some Difficulties, relating to that Subject, and
esteemed by him necessary to be satisfied, before any use could be made of
the said Instruments.
Upon this occasion, the Author of these _Tracts_ thinks fit, here to
represent, {229}
_First_, That _Englishmen_ and such others, as are well versed in the
_English_ tongue, find no difficulty in understanding the descriptions of
these _Engines_, nor in apprehending their structure, exhibited by the
_Figures_, especially if notice be taken of the Emendation, expressed at
the end of _Num._ 10. about the misgraving the _Bended end_ of the
_Springing Wire_ (which it seems has not been noted in _France_, tho' the
said _Num._ 10 is known to have been seen there a pretty while before their
_Journal_ of _May_ 24. was publish'd). And as for the particular of the
_Bucket_, fetching water from the bottom of the Sea, both the _Figure_ and
the annexed _Description_ thereof are so plain and clear, that 'tis some
wonder here, that any difficulty of understanding them is pretended by any,
that hath but ordinary skill in _Cutts_ and the _English_ language. Mean
while, that way, which the _French_ Author recommends for this purpose as
more simple, _Videl. a Brass-Pump with double Valves_, is not at all
unknown in _England_, nor has bin left untried there; but was found
inconvenient, in respect that the Valves in descending did not fully open,
and give the water a free passage through the Cavity of the Vessel, nor in
ascending shut so close, as to hinder the water from coming in at the top:
Whereas by the way proposed in _Num._ 9. both is perform'd with great ease
and security.
_Secondly_, Whereas the _French_ Author is of opinion, that 'tis unknown,
how much time a Heavy Body requires to sink in water, according to a
certain depth; he may please to take notice, that that hath been made out
in _England_ by frequent Experiments; by which, several Depths, found by
this Method of sounding _without_ a Line, were examin'd by trying them over
again in _the same_ place _with_ a Line, after the common way. And as to
that _Quaere_ of his, Whether a heavy Body descends in the same _Proportion_
of swiftness in _Water_, that it would do in _Air_? The Answer is, that it
does not; but that, after it is sunk one or two fathoms into the Water, it
has there arrived to its greatest swiftness, and keeps, after that, an
equal degree of velocity; the _Resistance_ of the water being then found
equal to the _Endeavour_ of the heavy Body downwards.
_Thirdly_, When the same _Author_ alledges that it must be known, when a
Light Body reascends from the bottom of the water to {230} the top, in what
proportion of time and swiftness it rises. He seems not to have considered,
that in this Experiment, the times of the descent and assent are both taken
and computed together; so that for this purpose, there needs not that
nicety, he discourses of.
_Fourthly_, Whereas it is further excepted, That this way of Sounding
Depths is no new Invention; The answer is ready, that neither is it
pretended to be so, in the often quoted _Tract_; it being only intimated
there, that the manner of performing it, as it is in that place represented
and described, is new.
_Lastly_, To rectifie the said Author's mistake, as if the instrument of
fetching up Water from the bottom of the Sea, were chiefly contriv'd, to
find out, Whether in some places of the Sea any _Sweet_ Water is to be met
with at the bottom: There will need no more, than to direct him to the Book
it self _Num._ 9. where p. 149. towards the end, the _First_ use of this
_Bucket_ is express'd to be, to know the _degrees of Saltness_ of the Water
according to its nearness to the top or bottom; or rather to know the
constitution of the Sea-water in several depths of several _Climates_,
which is a matter, much better to be found out by _Trial_, than
_Discourse_. Neither is it any where argued in that Book (as the _French
Journal_ insinuates) that, because sweet water is found at the Bottom of
the Sea of _Baharem_, therefore it _must_, but only that it _may_, be found
so elsewhere. And since the same _Journal_ admits, that those Sweet
water-springs, which yield the sweet water, that is found at the said
place, have been formerly on the _Continent_, far enough from the Sea,
which hath afterwards covered them. It will be, it is presumed, lawful to
ask, Why in many other places there may not be found the like? And besides,
how we do know, but that there may be in other parts, Eruptious of large
Springs at the bottom of the Sea, as well as there?
* * * * *
Printed with Licence for _John Martyn_, and _James Allestry_, Printers to
the Royal-Society. 1666.
{231}
* * * * *
_Num._ 14.
PHILOSOPHICAL
_TRANSACTIONS._
* * * * *
_Munday_, _July_ 2. 1666.
* * * * *
The Contents.
_An Account of a _New_ kind of _Baroscope_, which may be call'd
_Statical_; and of some Advantages and Conveniencies it hath above the
_Mercurial_; communicated by Mr. _Boyle_. The Particular Observations
of the Planet _Mars_, formerly intimated to have been made by Mr.
_Hook_ in _February_ and _March_ last. Some Observations, made in
_Italy_, confirming the former; and withall fixing the _Period_ of the
said Planet's Revolution. Observations, lately made at _London_, of the
Planet _Jupiter_: as also of _Saturn_. 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 the _Nile_, by Mons.
_de la Chambre_, both _French_: De Principiis & Ratiocinatione
Geometrarum, Contra Fastum Professerum Geometriae, by Mr. _Hobbes_: King
_Salomons_ Pourtraiture of Old Age, by_ J. Smith, M. D.
* * * * *
_An Account of a _New_ kind of _Baroscope_, which may be called _Statical_;
and of some Advantages and Conveniencies it hath above the _Mercurial_:
Communicated, some while since, by the Honourable _Robert Boyle_._
[Sidenote: * See _Num. 11. p. 185. Phil. Transactions._]
As for the _New_ kind of _Baroscopes_, 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 the
{232} Curious as much Information, as may be, in reference to _Baroscopes_;
I shall venture to send you some Account of what I did but name (in my
former Letter) to you.
[Sidenote: * _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 my
_Thermometrical 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 a _Glass-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 some _Glass-bubles_ as
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 their _AEquilibrium_ with 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 the _Mercurial_ Baroscope,
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 have {233} discerned far smaller Alterations of
the Weight of the Air, since I had the pleasure to see the Buble sometimes
in an _aequilibrium_ with 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 an _aequilibrium_, or a preponderance; so that I had oftentimes the
satisfaction, by looking first upon the _Statical_ Baroscope (as for
distinctions sake it may be call'd) to foretell, whether in the _Mercurial_
Baroscope 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 new _Baroscopes_
together, I shall add some of those Notes about this Instrument, which
readily occur to my memory, reserving the rest till another opportunity.
And _First_, if the ground, on which I went in framing this _Baroscope_, 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 a _Hydrostatical_ Law (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 another _Medium_, they will be no longer {234}
equiponderant; but if the new _Medium_ be heavier, the greater Body, as
being lighter in _Specie_, will loose more of its weight, than the lesser
and more compact; but if the new _Medium_ be lighter than the first, then
the bigger Body will outweigh the lesser; And this disparity, arising from
the change of _Medium'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 in _Mediums_ of differing gravity, or in the same _Medium_, in
case its (_specifick_) gravity were considerably alter'd: And consequently,
that since it appear'd by the _Baroscope_, 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, would _unequally_ affect 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 heavier _Medium_, 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 large _Orange_, 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 were {235} advantagious 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 the _Dryness_ and _Moisture_ of the
Air would in any measure have alter'd the weight of the Buble, as well as
the Variation of Gravity produced in the _Atmosphere_ by 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.