Mr. Walker on the artificial Production of Cold. 403 



powder, of which lie had procured ah adequate quantity, re- 

 peatedly recovered by evaporation over his hot iron plates, for 

 fresh use. 



I shall now present the immediate object of my present com- 

 munication ; viz. what I consider to be the best mode and fit- 

 test apparatus for cooling wine in summer, for freezing creams 

 in the small way for private use, and likewise for freezing a 

 small portion of water, merely as an experiment for public or 

 private exhibition. 



The drawing annexed (Plate VII.) is designed to represent 

 on a small scale the construction and exact proportions of 

 each freezing apparatus, and likewise the construction and 

 form of the apparatus for cooling wine. 



Fig. 1. is an apparatus for freezing water on the smallest 

 scale, as above mentioned, in the hottest weather. The vessel 

 for containing the freezing mixture is three inches and a half 

 in width, and its height equal in measure to its width; and 

 the tube for containing the water to be frozen five-eighths of 

 an inch in width, and reaching, as represented, very near to 

 the bottom of the vessel : there is likewise a rim or continua- 

 tion of the vessel, without a bottom, to insulate it from the 

 table or stand it rests upon. The apparatus itself consists of 

 two parts ; viz. the vessel for containing the freezing mixture, 

 and its cover, in one piece with the tube, fitting close over 

 it (represented together in the drawing). When the water is 

 frozen, upon taking off the cover and wiping the tube, the 

 solid ice will have become detached by the heat, and on in- 

 verting it drop out. 



The process may be known to be completed by the going 

 off or melting of the hoar-frost which exhibits a curious ap- 

 pearance outside the apparatus. 



Fig. 2. consists of an apparatus in one piece ; viz. the vessel 

 for containing the cooling mixture, and the cup or can (if I 

 may so call it) for receiving the decanter, its top rising some- 

 what above the height of the vessel for an obvious reason, with 

 a cover that will admit of easy removal (in the drawing repre- 

 sented together). This apparatus likewise has an appendage 

 or rim like the former, to insulate it from the table : — it may be 

 convenient to be possessed of a couple of these. 



Fig. 3. The apparatus for freezing creams, in which the 

 freezing mixture is to act on both surfaces of the part contain- 

 ing it, as being more ceconomical and expeditious, is not so 

 simple. This however consists only of two parts; viz. the vessel 

 for containing the freezing mixture ; and a cover, to which is 

 attached, in the same piece (instead of a tube or cup as in 

 fig. 1.), a concentric annular cavity or chamber, in which the 



3 F 2 prepared 



