and the Mode of its Communication. 75 



face of one of my large cylindrical passage thermom- 

 eters (No. 4) with that substance ; and, filling it with 

 boiling-hot water, exposed it to cool gradually in the 

 air of a large quiet room, in the manner often described 

 in former parts of this paper; another similar naked 

 standard instrument (No. 3 ) being filled with hot water at 

 the same time, and exposed to cool in the same situation. 

 The temperature of the air of the room being 51 J, 

 the instruments were found to cool through the stand- 

 ard interval of 10 degrees, namely, from loij to 91^, 

 in the following times : 



No. 4, covered w\\h. gold-beater's skin, . in 27! minutes. 

 No. 3, which was naked, . . . in 45 



Experiment No. 26. Being desirous of finding out 

 whether or not the covering of animal matter, which 

 had so remarkably facilitated the cooling of the instru- 

 ment No. 4, would be equally efficacious in facilitating 

 the passage of heat into the instrument, I suffered both 

 instruments to remain in the cold room all night ; and, 

 entering the next morning, at half an hour past seven 

 o'clock, I found the temperature of the water in the 

 naked instrument, No. 3, to be 50^; that in the instru- 

 ment No. 4, which was covered with gold-beater's skin, 

 was 49!- ; while the air of the room was at 48. 



At 7 h. 30 m. A. M. I removed both instruments into 

 a warm room, and observed the times of their acquiring 

 heat to be as expressed in the following table. 



Observed Temperature. Temperature 



Times when the obser- No. 3, No. 4, of the air of 



vations were made. naked, covered. the room. 



At 7 h. 30 rn. . . 50^ . . 49^ . . 64 



7 45 5* 5'i - 



8 ... . 52* 53* -65 



8 '5 531 - 54i 



