the Production of artificial Cold. 129 
These experiments were made in such an apparatus as I am 
going to describe, which may at first appear new, but, upon 
examination, will be found to be only a different modification 
of the vessels represented in Fig. 3 and 4, Tab. XXIII. of Phil. 
Trans, for 1795; and appears to me to have all the advantages 
that can be obtained in an experiment of this nature. 
Plate VIII. Fig. i, represents the section of an apparatus, con- 
sisting of two vessels ; viz. A A, is a vessel 4 inches in diameter, 
and 4 inches high, (omitting its stand, by which it rests over 
another vessel, presently to be described,) having a tube (of one 
piece with it) a, £ and ~ in diameter, and 4 inches deep. This 
tube has a horizontal rim or shoulder, at - of an inch from the 
top,* and is open at both ends ; the lower one being closed 
occasionally, in the manner hereafter to be described ; and 
the top of the tube, when the apparatus is of glass, by a 
stopple ; or, if constructed of tin, by a sliding cover, fixed on 
the lid C. 
C, is the cover or lid of this vessel, fitting over it quite close, 
and having a collar to fit over the tube, likewise, down to 
its shoulder. 
B, represents a second vessel, upon which the former fits 
closely, but not tight. This vessel is 3 inches and f in height, 
having a conical cup (of one piece with it) 6, 1 inch and 
diameter at the top, and 1 inch in diameter at the bottom, 
and three inches in depth : this cup is inclosed, at the distance 
* This vessel, when used, is to be filled up to this rim or shoulder only ; that serving 
as a guard to prevent the frigorific mixture from getting into the tube : hence, the 
capacity of the vessel ending here, its height, and that of the tube, may be considered 
as 3 inches and ®. 
MDCCCI. 
S 
