The works of the Honourable Robert Boyle, Esq., epitomiz'd by Richard Boulton ... ; illustrated with copper plates.

TITLE IV. Experiments and Observations concerning the degrees of Cold in several Bodies.

TO discover the different degrees of Cold we have proposed several Thermometers in the preceeding Chapters, concerning which we shall add this Advertisement viz. That tho' those which are to be immersed in Liquors, have the Ball end round; yet, when we are to try the degrees of Cold of consistent Pow∣ders, it is better to make use of such as have flat Bottoms, that they may be able to stand on their own Basis: For so it will be pleasant to see the suspended Bubble in one of our Thermo∣meters rise and fall, as it is removed from one Body to another.

2. Freezing hath been so generally esteemed, the utmost Effect of Cold, That most have been content, without examining strictly the several degrees of it. Nor indeed is it very easily done, since if we do it with common Weather-glasses it will be a hard thing to distinguish whe∣ther the Cold of one Day, exceeds that of a∣nother; since there intervening so much time betwixt the Observations, the Alterations may be caused by an increase in the weight of the Atmosphere. And should we make an estimate by the Testimony of our Senses, we should easi∣ly be mistaken; since it is believed, That the different sensations of Cold which we perceive, depend on the various Dispositions of our Bo∣dies.

But allowing, that vulgar Thermometers might give us a true Information of the degrees of Cold, which Nature affords, yet they ac∣quaint us not whether Art may not produce greater; much less will they help us to make an estimate of this Disparity. And though we may make some guess by the Operation of Cold on Liquors exposed to it, yet some as A∣queous Liquors freeze too soon, and vinous Li∣quors here in England will not freeze at all, ex∣cept French Wine; which happens seldom and leaves too great an Interval betwixt the degrees necessary to congeal Wine, and sufficient to freeze Water, besides the uncertainty proceed∣ing from the several strengths of Wines.

Wherefore to discover the Intensity of Cold, produced by Art above the highest degree that Nature affords, we furnished a sealed Weather-glass (Such as Plate 1. Fig. 1. Delineates) with Spirit of Wine, and immersed the Ball and part of the Stem in a Vessel of Water, which was half buried in Snow and Salt, and when the Water began to freeze at the bottom and a∣bout the sides, the Liquor was Subsided to 5 2/•• Di∣visions, each Division being half an Inch; and then the Weather-glass being taken out of the Water and applied to the Snow and Salt, it Subsided to 1 ½ Division.

To this we shall add another which shews, That the Water tho' froze was warmer than the Spirit of Wine, when the Mixture of Snow and Salt was applied to it. Jan. 15 the Wea∣ther-glass being kept in the Water till it began to freeze descended to 5 ½ but being removed into the Snow and Salt it Subsided first briskly

and then more gradually till it sunk to the Bottom of the Stem; but being removed into the Water again, it ascended to the same height, the Water had before depressed it to.

For a further Tryal, how much Liquors may be condensed by Cold, we took Oyl of Tur∣pentine rectified in a gentle Heat, and having weighed a Glass-ball with a long Stem, it being one Ounce, one Dram, five Grains and a half; we poured on it so much of the Turpentine as in∣creased the weight to, two Ounces seven Drams and thirty four Grains and a half; which reach∣ing a little way into the Stem, we marked the Superficies with a Diamond; after which we poured a Dram more in, and successively more; still marking how high each Parcel, which was weighed exactly, rought in the Stem, till the Additional weight increased the former to three Ounces, one Dram, four Grains, and a half; and then taking a wide-mouth'd Glass with Water in it, we immerged the Weather-glass in the Water as before; the Vessel in which it was contain'd being first encompass'd with Snow and Salt: When the Water began to freeze, we mark'd the Stem of the Glass which contain'd the Oyl at the place to which it subsided; and then conveying it into a Mixture of Snow and Salt, when it had subsided as low as it could, we mark'd the Superficies, and then remov'd it into the Air, till it rose to it's first station; and then we pour'd so much of the Oyl out into a∣nother Glass carefully poised in a pair of Scales, that the Superficies of the Oyl remain'd at the Mark which it subsided to in the Water; and we found that the Oyl poured off weigh'd a∣bout

10 Grains: And so much more being pour'd off as made it stand at the Mark to which the Snow and Salt depress'd it, it weigh'd about as much as the former; so that the Oyl was Ar∣tificially condensed, so far, That it subsided as much after it had been condensed by Cold strong enough to freeze Water, as it was caus∣ed to fall by the force of that. And by divid∣ing the whole Proportion of Oyl, by the num∣ber of Grains whose Bulk it seem'd to lose by subsiding in Water, we found that it was con∣densed by the first degree of Cold to a 94th Part of it's Bulk and by dividing it by the Ad∣ditional number of the Grains more, we found that the Snow and Salt had condensed it a 47th Part of it's Bulk.

Having circumscrib'd Water moderately Cold with a Mixture of Snow and Salt, what it shrunk was, if not insensible, inconsidera∣ble.

To measure the differing weight and Density of the same Proportion of Water, in the Heat of Summer and when extremely Cold; we weighed a Glass-Bubble in it, which was Hea∣vier than Water moderately cool, and by the Diminution of it's weight in that Medium; we found, according to the Rules of Hydrostaticks, the weight of a Portion of Water of equal Bulk: And then weighing it in Water cool'd, by a Mixture of Snow and Salt, we were inform'd by a new Decrement of it's weight, of the weight of an equal Bulk of that Cold Water; by which we were enabl'd to make an Estimate of the Gravity and Density acquired by the Action of Gold, and by weighing the same Bubble in the

same Water in hot Weather, we Learnt further how much more dense and heavy Water mode∣rately Cold and extremely Cold, is than warm Water. It would be of use to try such Experi∣ments as these in Italy, where they have the Conveniency of keeping Snow, and of freezing warm Water speedily. A Glass-Bubble which in the Air, weighed 150 Grains being weighed in Water; on a Day not frosty, it weighed 29 ••/8 and being weighed in Water which was a little froze in a Mixture of Snow and Ice, it was not above ⅛ Part of a Grain lighter than before; so that the Water by Condensation lost not above a 230th Part of it's former Bulk. How far it may be of use at Sea to make such Experiments as these, and whether they may thereby learn to know, by finding the Density of the Water in several Places; what Loads to carry in their ships and what the Water will be able to bear, I shall leave others to Judge: But if such Experiments be try'd in several Parts; our Seal'd Weather-glasses, or that which contains the Pendulous drop of Water, may be of use; since they not being subject to be varied by the Alterations in the Atmosphere's Gravi∣ty, and since they may be conveniently carried from one Country to another, the different de∣grees of Cold in various Regions may be better Estimated; a Register being kept of the de∣grees the Liquor or Pendulous drop stood at such times as the Tryals were made and where, and when exposed to such a degree as was a∣ble to freeze. To conclude this Title I shall add, that in making these Experiments, with the Ther∣mometer

in which the Pendulous Water is con∣tain'd; the Stem may, for conveniency, be held either Horizontal, upwards or Perpendi∣cular.

Notes

• Of the de∣grees of Cold in several Bodies.
• See Plate. 1. Fig. 1.