20 Abstract qffeCent Researches on the quantity of 



pied with researches of this kind, and the attention of the 

 Academy of Sciences having been directed thereto by M. Hess, 

 who had had conversations with Dulong on the subject, the 

 manuscripts which he left behind were examined by Arago, 

 and the following results obtained. Dulong had made an 

 extensive series of experiments on the quantity of heat evolved 

 in combustion, but did not write out any full description of 

 his apparatus or methods; M. Cabart, however, who had 

 been working in Dulong' s laboratory, was able to describe the 

 form of calorimeter which had been used. A rectangular box 

 in red copper, of 25 centimetres in depth, 7*5 in breadth, and 

 10 in length, is the space in which the combustion is carried 

 on ; the oxygen or other gas supporting the combustion is 

 introduced by a tube, and the products of combustion carried 

 off by another. For the precise arrangement of these tubes, 

 which are complicated in their form, for the purpose of recei- 

 ving the thermometers by which the temperatures are read off, 

 we must refer to the original. This box is immersed in a 

 vessel holding eleven quarts of water. In this box gases 

 were burned by means of jets, of various sizes, according to 

 the combustibility of the gases. The liquids were burned by 

 means of a few cotton threads in a glass tube closed at one 

 end : it is not known how they were set on fire. The solid 

 bodies (except iron, which was used in coils of fine wire) were 

 in the state of powder, and were set on fire by a bit of amadou. 

 The following tables give the most important results ob- 

 tained by Dulong; the unity of calorific effect employed 

 being the quantity of heat necessary to raise the temperature 

 of a gramme of water one centigrade degree at ordinary 

 temperatures. 



Substances and quantities Quantity of heat evolved in 



employed. combustion. 



Max. Min. Mean. 



One litre of hydrogen, five"! 



experiments J 



One litre of pond gas, fourl 



experiments J 



One litre of olefiant gas, 1 ^ 15338 



five experiments J 



One litre of carbonic oxide,! j 



three experiments ... .J 

 Carbon, equivalent to one | 



litre in gaseous state, > 8040 7540 7858 



four experiments J 



Alcohol, one litre in ya- 1 u j u fo 



pour, two experiments. J 



