VOL. LV.] PHILOSOPHICAL TRANSACTIONS. 239 



cessive hot weather, filled with Pouhon water, with a bladder fitted to it, as re- 

 lated in the foregoing experiments. The phial thus filled was placed in a copper 

 vessel, so as to be immersed in water to f of its height; and to the neck of the 

 phial was fitted a kind of truncated cone of spiral wire, to keep the bladder in an 

 erect position. The copper vessel was set over a slow fire, and the water therein 

 heated to as great a degree as he could well endure with his hand; which he 

 found to be about 1 ] degrees, according to Fahrenheit's scale. In this degree 

 of heat, large bubbles of air soon began to arise to the top of the phial, forcing 

 up with them small particles of water, which bedewed the sides of the bladder 2 

 inches or more in height. The phial being taken for a few moments out of the 

 bath, the more exactly to view this kind of ebullition, very minute bubbles were 

 observed to be formed, in the middle of the water, near the bottom of the phial ; 

 and from thence ascending with a rapid motion, and in continued streams, gra- 

 dually to enlarge, until they fiew off, with a boiling motion, and considerable 

 force, from the surface of the water, which by its dilatation, arose from the 

 bladder. The phial was kept in this moderate heat 2 hours, during which time 

 the bladder became more and more distended with the air, or other elastic sub- 

 stance expelled from the water; which was observed to acquire a muddy whiteness 

 in proportion as the elastic substance was expelled from it. The bubbles, after 

 about 1-i^ hour, gradually lessened in number and size, and at the end of 2 hours 

 almost disappeared. The heat was then gradually increased for another hour ; at 

 the end of which time the water in the copper vessel began to boil. And in this 

 boiling heat the phial remained another hour; when it being judged that all the 

 elastic substance contained in the water was expelled from it, the phial was removed 

 from the fire, after it had continued in the water bath 4 hours. From the time 

 that the heat of the bath was increased, the water in the phial grew more and 

 more turbid; the earthy particles were formed into small masses, whi<:h were 

 driven about by the heat. Towards the end of the operation, these earthy masses 

 cohered into larger flocculi: and from white became of a yellowish colour. 

 These flocculi grew larger as the water cooled, and slowly subsided to the bottom 

 of the phial. While the water in the phial was yet warm, the elastic substance 

 that had been expelled from it was tied up close in the bladder, and then removed 

 from the phial. The water in the phial being corked up, was suffered to stand 

 till perfectly cool. Being then examined, it was found to have got a taste from 

 the bladder; but was quite vapid, having entirely lost its distinguishing brisk, 

 sharp, ferruginous taste, as also its power of striking a purple colour with galls. 

 The elastic substance contained in the bladder, when taken from the fire, ap- 

 peared equal in bulk to 4- a pint of water. It lessened considerably in the cool 

 air, for some days after it had been thus extracted, but did not afterwards seem 

 to diminish much in bulk, though kept for a month in the bladder. 



