232 Historical Review of Experiments 



cone be held in the neighbourhood of and towards an 

 object which is giving off calorific (or frigorific) rays, 

 the heat (or cold) caused by these rays is communicated 

 to the fluid contained in the space between the two 

 cones, and this change of temperature brings about a 

 corresponding change in the level of the liquid in the 

 upper part of the tube ; by this means the amount of 

 heat (or cold) communicated can be estimated and 

 measured. 



An instrument of this description, which I procured 

 in the year 1801, during my stay in England, is at 

 present in the physical cabinet of the Royal Institu- 

 tion at London. Two similar ones, fitted up in Bava- 

 ria, are still kept in my cabinet at Munich. I have 

 described this instrument thus minutely, simply because 

 I am convinced that it is of very great service in ex- 

 periments on the calorific and frigorific radiations from 

 various bodies, and because it has been my earnest de- 

 sire to induce natural philosophers to devote their atten- 

 tion to this subject, so worthy of investigation. 



It only remains for me to say a few words in regard 

 to the experiments which I have described very fully 

 in the memoir read before the Royal Society on the 

 ^d of February, 1804, which has been translated into 

 French by Professor Pictet.* 



I performed these experiments in Munich, in 1803, 

 during the months of January, February, and March. 

 According as the results seemed of importance, I imme- 

 diately acquainted my friends in England and France 

 with -them. Among others, I communicated to Sir 

 Joseph Banks, then President of the Royal Society of 

 London, the very striking results of an experiment 



* See page 23. 



