Micrographia - Some Physiological Descriptions of Minute Bodies Made by Magnifying Glasses with Observations and Inquiries Thereupon by Robert Hooke
page 109 of 465 (23%)
page 109 of 465 (23%)
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cold Water, does make the parts of the Glass suffer a double contraction:
The first is, of those parts which are neer the Surface of the Drop. For Cold, as I said before, contracting Bodies, that is, _by the abatement of the agitating faculty the parts falling neerer together_; the parts next adjoyning to the Water must needs lose much of their motion, and impart it to the Ambient-water (which the Ebullition and commotion of it manifests) and thereby become a solid and hard crust, whilst the innermost parts remain yet fluid and expanded; whence, as they grow cold also by degrees, their parts must necessarily be left at liberty to be condensed, but because of the hardness of the outward crust, the contraction cannot be admitted that way; but there being many very small, and before inconspicuous, bubbles in the substance of the Glass, upon the subsiding of the parts of the Glass, the agil substance contained in them has liberty of expanding it self a little, and thereby those bubbles grow much bigger, which is the second Contraction. And both these are confirmed from the appearance of the Drop it self: for as for the outward parts, we see, first, that it is irregular and shrunk, as it were, which is caused by the yielding a little of the hardened Skin to a Contraction, after the very outmost Surface is settled; and as for the internal parts, one may with ones naked Eye perceive abundance of very conspicuous bubbles, and with the _Microscope_ many more. The Consideration of which Particulars will easily make the Third Position probable, that is, that the parts of the drop will be of a very hard, though of a rarified Texture; for if the outward parts of the Drop, by reason of its hard crust, will indure very little Contraction, and the agil Particles, included in those bubbles, by the losing of their agitation, by the decrease of the Heat, lose also most part of their Spring and Expansive power; it follows (the withdrawing of the heat being very sudden) that the parts must be left in a very loose Texture, and by reason of the |
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