110 



Till' law of (.'ooliiin' was soon suhjcclcd to cxpcriinciital 

 tests, 'i'lir classical vcrilicalioii is llial ot" Kiclimaiui (the 

 law itself is often called l\icliniaiiii's law). Marline, in 

 1740, ol)served that for a ^ood aureenient between the 

 theoretical law and the e\|)('riineiital data the tenipei'al ni'e 

 of t he object shonld not dilfer from that of the ])atli by more 

 than al)ont 50°. Dalton showed that the cooling velocity 

 is in reality more rapid than that indicated by Newton's 

 law. Dnloiii; and Petit, in 1817, nndi'rtook to establish 

 more accurately the influence of each factor on the rate of 

 cooling. They proposed corrections to render the formula 

 applical)le ov^er a larger range of temperatures. Other 

 corrections were introduced later by other investigators. 

 But the fundamental law established by Newton, although 

 correct only in a first approximation, is still usually em- 

 ployed in most of the practical applications, ((^f. Chajj- 

 puis and Berget : "Legons de Physique Generate." Paris, 

 1911, Vol. I, p. 622.) 



Perhaps, when erroneous conclusions are drawn from 

 the application of the law of cooling, it is not so much on 

 account of its lack of accuracy but because some of the 

 conditions for its application are not fulfilled; for example, 

 the object to be cooled may not be entirely surrounded by 

 the bath, as when use is made of a too bulky thermometer- 

 stem or of too conductive thermocouple-leads which estab- 

 lish thermal connections with the outside. 



All the problems so far treated have been analysed as 

 particular cases of the original assumption of an ideal wall 

 limited by two surfaces at constant temperatures. In many 

 instances one or both of these temperatures vary. There 

 results a large number of possible problems to be analysed 

 by further application of the method of simplifying 

 assumptions. 



SUMMARY 



The essential points l)rought out in the preceding ])ages 

 can be summarized as follows: 1. ]\Iost of the investi- 

 gations 01] thermometry and calorimetrv to be described 



