qQ philosophical transactions. [anno 1084. 



in hot and frosty weather, it may then be said to be in a natural state, free, 

 open, and expanded, which it seems it always is within the tropics, and with us 

 only in very hot, and very frosty weather. But when it descends, it is then 

 contracted, as it mostly is in our climate of England, and probably more or less 

 so in all places on this side the tropics. Which contraction plainly appears from 

 the concave figure of both surfaces, viz. of the quicksilver in the tube, and of 

 that which stagnates in the cistern. The difficulty seems to lie in the recon- 

 ciling the same effect of the quicksilver rising in the tube, from such seemingly 

 differing causes, as great heat and intense frost; for those who willingly assent 

 to us in one particular, and grant that warmth is a probable cause of its resti- 

 tution to its nature, may yet doubt how great frost likewise should do the same. 

 I answer, that salts liquefied will coagulate or crystallize, that is, will return to 

 their own proper natures, both in cold and in heat ; and therefore, though 

 most men practise the setting them in a cool cellar for that purpose, yet some, 

 as Zwelfer, advise, as the best means to have them speedily and fairly crystal- 

 lised, the keeping them constantly in balneo. Thus also the lympha of the 

 blood becomes a jelly, if set in a cool place, and it is likewise inspissated by 

 warmth. Again, it is no new opinion that water is naturally ice. And Borri- 

 chius, the learned Dane, has said something for it; and I may venture to add, 

 in confirmation of that doctrine, that salt is naturally rpck, that is, naturally 

 fossile, not liquid; and yet this is most like ice of any thing in nature; not 

 only on account of its transparency, but also for its easy liquefaction, and the 

 sudden impressions and changes the air makes upon it; so that it is scarcely to be 

 preserved in its natural state of crystallization. Also salts of all sorts seem na- 

 turally to propagate themselves in a hard state, and to vegetate in a dry form. 

 The like is to be observed in quicksilver, of its being a hard rock, and also 

 from its willingness to embrace upon all occasions a more fixed state, as in its 

 amalgamizing with almost all sorts of metals. 



If therefore quicksilver and liquids are nearest their own natures, and suffer 

 less violence in very cold and very hot seasons; the humours of our bodies, as 

 liquids, must probably, in some measure, be affected accordingly. And that 

 therefore cold is healthful, I argue from the vast number of old men and women 

 to be found on the mountains of England, comparatively to what are found 

 elsewhere. Again, the blood itself, or the vital liquor of animals equivalent to 

 it, is in most kinds of animals sensibly cold; for the species of quadrupeds and 

 fowls are not to be compared for number to fishes and insects; there being in 

 all probability above 100 species of these latter creatures whose vital juice is 

 cold, to one of the former ; but because we most converse with those whose 

 vital juice is hot, we are apt to think the same of all. 



