Memoirs for the natural history of humane blood, especially the spirit of that liquor by Robert Boyle.

Experiment. II.

HUmane Urine, having first (that I know of) by the very ingenious Mr. Hook, and often∣times by me, been observ'd, when frozen, to have on the surface of the Ice, figures not ill resembling Combs or Feathers; the great affinity gene∣rally supposed to be betwixt Ʋrine and the Serum of Blood, made me think fit to try at once whether this last nam'd Liquor would freeze with such a degree of Cold, as would easi∣ly, and yet not very easily glaciate water, and whether, in case it should freeze, the Ice would have a surface figur'd like that of frozen Urine. But, having for this purpose exposed some Serum of Humane Blood to the Cold Air, in two freezing nights

consecutively, the Serum was not found to congeal, tho some Grumous parts of the same Blood did, as has formerly been noted, yet I scarce doubted, but an exceeding hard frost would have produc'd, at least a thin Plate of Ice upon the surface of our Liquor. And to confirm this Con∣jecture, we took the same Serum, and having strained it through a Lin∣nen cloath, to separate the Liquor as much as by that way we could, from any clotted or Fibrous Parts, that might have lain conceal'd in it, we put it into a shallow, concave glass, and laid that upon some of our Frigorifick mixture, made of Ice and Salt, which we have described, and often made use of, in the History of Cold. By this means the exposed Serum, being frozen from the bottom upwards, there appeared here and there upon the Ice contiguous to the Air, cer∣tain Figures, that did not ill resem∣ble those of Conglaciated Urine.