1885.] Mr. Coleman and Prof. McKendricJc on Cold, dc. 305 



WEEKLY EVENING MEETING, 



Friday, May 29, 1885. 



William Huggins, Esq. D.C.L. LL.D. F.R.S. Manager and 

 Vice-President, in the Chair. 



J. J.. Coleman, Esq. F.C.S. F.I.C. and Professor J. G. McKendrick, 

 M.D. LL.D. F.E.S. 



The Mechanical Production of Cold and the Effects of Cold upon 

 3Iicrophytes. 



This discourse was delivered by Mr. J. J. Coleman, and embraced 

 two parts, viz. 1st, a description of his own researches and their 

 application in the construction of cold-producing machines ; and 

 2nd, a description of a joint research undertaken by Professor 

 McKendrick and himself upon the effects of very low temperatures 

 upon microphytes. 



Mr. Coleman pointed out that in the first place the title of the 

 discourse might be objected to, inasmuch as it was scarcely correct 

 to speak of the " production of cold." As, however, long usa«e had 

 made the phrase conventional it would be used in the sense of 

 meaning production of a state of coldness. 



A close examination of all known methods of producing cold by 

 artificial means involved the employment of some volatile liquid 

 or compressed vapour capable of spontaneously expanding. Thus, 

 commencing with water, its spontaneous evaporation produced the 

 state of coldness of the domestic water-cooler. 



The evaporation of ether, as in the spray used by surgeons ; also 

 the evaporation of liquid sulphurous acid, which boiled at — 10° C. • 

 of liquid carbonic acid, which boiled at — 78° C. ; of liquid nitrous 

 oxide, which boiled at — 86° C; of liquid ethylene, which boiled at 

 ~ 102° C. ; or of liquid air, which boiled at - 191° C, were all 

 perfectly analogous to the spontaneous expansion of compressed air, 

 when released from pressure by opening the cock of a vessel 

 containing it. 



The nearer the compressed vapour is to the state of a perfect 

 gas, or of a hypothetical perfect gas, the more exactly is the heat 

 absorbed by expansion balanced by the heat generated by the friction 

 of the molecules before coming to rest. This followed from the 

 joint researches of Sir William Thomson and Dr. Joule conducted 

 thirty years ago.* These eminent men, in a classical series of 

 experiments, the description of which occupies 122 pao-es of Sir 



* " On the Thermal Effects of Fluids in Motion." See collected papers of Sir 

 W. Thomson, vol. i. Cambridge University Press, 1882. 



Vol. XL (No. 79.) ' x 



