on the Subject of Heat. 225 



It is only necessary to see this apparatus, which I 

 had made in the summer of 1801, to be immediately 

 convinced that I pursued my researches on the subject 

 of heat zealously and connectedly. 



In the beginning of the year 1802 I was recalled to 

 Bavaria. I was, therefore., obliged to leave London in 

 the early part of the month of May, after I had actually 

 begun on a very few only of the experiments which 

 I had planned with so much pains. But as I was 

 firmly resolved to devote myself to them again, as soon 

 as I could obtain any leisure, however little, I took 

 back to Germany with me the greater part of this ap- 

 paratus which I had procured during my stay in Eng- 

 land. 



During my journey, I remained three months at 

 Paris, so that I did not reach Munich before the end 

 of August. In the early part of the month of October, 

 however, I began my experiments. 



As I had not been able to bring with me from Lon- 

 don the four large reflectors belonging to the Royal 

 Institution, and as I could not procure similar ones 

 in Bavaria, I was obliged to change the plan of my 

 investigations, and to try whether it might not be pos- 

 sible to discover the radiation from bodies in some 

 other way, and to make the effects of these radiations 

 manifest without the aid of the concentration brought 

 about by means of the metallic reflectors. 



In the first experiments which I undertook, I had 

 this object in view, to determine whether the invisible 

 heating rays which a warm body (a heated stove, for 

 example) gives out are not of the same character as 

 those coming from the sun. For this purpose I pro- 

 cured three cylindrical boxes of very thin, soft wood, 

 VOL. ii. 15 



