2J2 On the ProduSlion of artifclal-Cold. 



Befides thefc interefting fa£ts, this memoir contains other analyfes which are very well 

 made, of fubftances of cotifequencc to feveral arts and to medicine, as to the accuracy of 

 their proportions. 



'The commiflaries are therefore of opinion that the clafs fliould order it to be printed in 

 the volumes of the Savans Etrangers;_and that Citizen Thenard would render a great 

 fervice to chemiftry by continuing to employ himfelf on the fame plan upon thefe com- 

 plex combinations of which difierent natural bodies are fufceptible; this important objcfl 

 having been hitherto too much neglected by chemifts. 



VII. 



On tke Produclion of artificial Cold by Means of Muriate of Lime. By Mr. RiCHAKO 

 Walker. (Phikf. Tra?f. i8oi.> 



{Concluded from page %t'].) 



i LATE XII. Fig. I, reprefents the fe£l:ion of an apparatus, corififting of two veflels ; 

 ▼iz. A A, is a veffel 4 inches in diameter, and 4 inches high, (omitting its ftand, by which 

 it refts over another veflcl, prefently to be defcribed,) having a tube (of one piece with it) 

 a, I and i in diameter, and 4 inches deep. This tube has a horizontal rim or flioulder, 

 nt -f- of an inch from the top, * and is open at both ends ; the lower one being clofed occa- 

 fionally, in the manner hereafter to be defcribed ; and the top of the tube, when the ap- 

 paratus is of glafs, by a ftopple; or, if conftru£lcd of tin, by a Hiding cover, fixed on the 

 lidC. 



C, is the cover or lid of this veflel, fitting over it quite clofe, and having a collar to fit 

 over the tube, likewife, down to its flioulder. 



B, reprefents a fecond veffel upon which the former fits clofely, but not tight. This 

 Teffel is 3 inches and f- in height, having a conical cup (of one piece with it) b, i inch and 

 Y diameter at the top, and i inch in diameter at the bottom, and three inches in depth : 

 this cup is inclofed, at the diflancc of -f of an inch, by a thin partition c c,\ of one piece 

 likewife with the veffel. 



• This veffel, when ufed, is to be filled up to this rim or flioulder only; that ferving as a guard to pre- 

 vent the frigorific mixture from getting into the tube : hence, the capacity of the veffel ending here, its 

 height, and that of the tube, may be confidered as 3 inches and |.. 



+ Having afcertained by experiment, that a ftratum of air of this thicknefs did not prevent (during the 

 length of time which is required to freeze ihe water, and reduce the ice to powder in the tube a) the materials 

 in the cup h from receiving the temperature required, yet was neverthelefs fu'fficient to impede the aftion of 

 ifce mixture oil the materials, when mixed In'the cup b, during \.\\efliort time required to take its temperature, 

 or to freeze the quickfdver, 1 adopted this method, in preference to letting out the frigorific mixture from 

 the veffel B, immediately before mixing the laft materials, as formerly. 



