No. 17. {From Nature, May 12, 1898, Vol. L VIII, p. 30.] 



NOMENCLATURE AND NOTATION 

 IN CALORIMETRY 



ALL who are engaged in thermal investigations them- 

 selves as well as those who have occasion to study the 

 published work in this department of science, must have 

 been frequently annoyed by the use of the word calorie with 

 its varying signification. It has been sought to remove the 

 inconvenience by qualifying the calorie as small or great, and 

 in other ways ; but on opening a book at any place where 

 the results of thermal determinations are given, it is in most 

 cases difficult to discover at once what unit of heat the author 

 is using. 



As different classes of investigation are carried on on 

 different scales, it is obvious that it is a convenience, if not 

 a necessity, to have different heat units at disposal. The 

 unit which is suitable to express the thermal changes in a 

 beaker in the laboratory would manifestly be inconvenient 

 when dealing with the daily or seasonal changes in a lake or 

 an ocean. It is therefore natural and necessary to have heat 

 units of different magnitudes, but it is neither natural nor 

 necessary to call them all by the same name, and it is ex- 

 tremely inconvenient not to have a short form of notation 

 which will show on its face the actual heat unit used. 



In the early literature of the equivalence of heat and work 

 in this country, one unit of heat is universally used ; it is 

 the pound-degree-Fahrenheit, and in the writings of Joule, 

 Thomson, Rankine and others of that time it is simply called 

 " heat unit," as there was no other competing with it. With 

 the rise and development of thermal chemistry, it was neces- 

 sary to fashion the compound unit out of the simple units in 



