6 Mr Parker, On Ganiot's principle [Oct. 31, 



The accuracy of the corrections is indicated by the close agree- 

 ment amongst the results deduced from thermometer N, for its 

 coils differ greatly in length and resistance. On reference to 

 my 1890 note-book I find that thermometer H was made of a 

 special sample of wire, which was supposed to be of greater purity 

 than the samples previously supplied, and judging by results, it 

 appears that the assumption as to its purity was justified. It 

 is probable that small traces of impurities could be detected by 

 an application of the above method, and I have little doubt but 

 that the considerable divergence from the mean shown by those 

 values of t deduced from thermometer M, are due to the presence 

 in its coils of other metals than platinum. 



(2) Carnot's principle and animal and vegetable life. By 

 J. Parker, M.A., St John's College. 



It is commonly stated that an animal has a much greater 

 ' efficiency ' than a Carnot's perfectly reversible engine working 

 through the same range of temperature ; and it is even com- 

 pared to an electro-magnetic engine, though there are generally 

 no sensible electric manifestations about the animal body. In 

 consequence it is believed that the changes which take place 

 in the animal world are not subject to the restrictions of Carnot's 

 principle. Hence since Carnot's principle is universally applic- 

 able to inanimate objects, it will follow that the laws of nature 

 are not the same for living things as for the rest of the universe. 

 The whole difficulty, however, arises from an oversight, and can 

 be removed with a little care. 



In order that Carnot's principle should be applicable to a 

 material system, two conditions are necessary : — 



(1) The system must always contain the same matter, so 

 that matter must neither be allowed to enter the system nor 

 leave it, 



(2) The system must gain or lose energy only in the forms 

 of heat and mechanical work. The interior of the system may 

 be electrified or magnetized in any way we please, but the system 

 must produce no electric or magnetic effects on external objects, 

 nor have any electric communication with them. 



If the first condition is fulfilled, but not the second, the system 

 is an electro-magnetic engine. Carnot's principle is then not 

 generally applicable, nor the principle of energy in its usual form 



dU=dQ + dW. 



The difference between an electro-magnetic and a heat engine 

 is well illustrated by taking as pur system two pieces, AP, BP, 



