(261)
come to be clogg'd in their motion: Whence it seem'd reasonable to expect that upon the Reunion of the Saline particles into such a Body, as they had constituted before, the redintegrated Sal Armoniack having, neer upon, the same Texture, would, upon its being redissolv'd, produce the same, or a not much inferior degree of Coldness: And hereupon, though I well enough foresaw that an Armoniack solution, being boyl'd up in Earthen vessels (or Glass ones are too chargeable) would, by piercing them, both lose some of the more subtle parts, and thereby somewhat impaire the texture of the rest; yet I was not deceiv'd in Expecting, that the dry Salt, remaining in the pipkins, being redissolv'd in a due proportion of water, would very considerably infrigidate it, as may further appear by the Notes, which for your greater satifaction you will find here subjoyn'd, as soon as I have told you, that, though for want of other vessels I was first reduc'd to make use of Earthen ones, and the rather, because some Metallin Vessels will be injur'd by the dissolv'd Sal Armoniack, if it be boyl'd in them, yet I afterwards found some conveniences in Vessels of other Mettall, as of Iron; whereof you may command a further Account.
March the 29th, the Thermoscope in the Air was at 878 inches; being put into a somewhat large evaporating glass, fill'd with water, it fell (after it staid a pretty while, and had been agitated in the liquor) to 8. inches: then about half the Salt, or less, that had been used twice before, and felt much less cold than the water, being put in and stirr'd about, the tincted Spirit subsided with a visible progress, till it was faln manifestly beneath 4. inches; and then, having caused some water to be freshly pump'd and brought in, though the newly mention'd Solution were mixt with it, yet it presently made the Spirit of Wine manifestly to ascend in the Instrument, much faster, than one would have expected, &c.
And thus much may suffice for this time concerning our Frigorifick Experiment; which I scarce doubt but the Cartesians will lay hold on as very favourable to some of their Tenents; which you will easily believe, it is not to the Opinion, I have elsewhere oppos'd, of those Modern Philosophers, that would have Salt-petre to be the Primum Frigidum: (though I found by trial, that, whilst 'tis actually dissolving, it gives a much considerabler degree of Cold, than otherwise.) But about the Reflexions, that may be made on this Experiment, and the Variations, and Improvements & Uses of it, though I have divers things lying by me; yet, since you have seen several of them already, and may command a sight of the rest, I shall forbear the mention of them here, not thinking it proper, to swell the bulk of this Letter with them.
1. EUCLIDIS ELEMENTA GEOMETRICA, novo ordine ac methodo demonstrata. In this compendious and pretty Edition, the Anonymous Author pretends to have rendred these Elements more expeditious; by bringing all together into one place, what belongs to one and the same subject: Comprising 1. what Euclid hath said of Lines, Streight. Intersecting one another, and Parallel.2. What he hath demonstrated of a Single Triangle, and of Triangles Compared one with another.3. What of the Circle, and its Properties.4. What of Proportions in Triangles and other Figures.5. What of Quadrats and Rectangles, made of Lines diversly
