FROM WOOD AND (OIL. \; 



of heat will therefore be equal, in equal periods of time, m all 

 the experiments, by which the objections made against the plan 

 of Count Rumford s experiments are considered as obviated. 



The manner of experimenting is as follows 



The first step to be taken by the operator, is to produce tin 

 required difference of 10° between the interior and exterioi 

 rooms, and to arrange the necessary coincident circumstances 

 for its perpetuation. 



As no artificial refrigerating means can. with Convenience, 

 be made use of to depress the temperature of the exterior room 

 below that of the atmosphere, it becomes necessary thai tin 

 temperature of this room shall, in the first instance, be highei 

 than any elevation which will occur in the temperature of th( 

 atmosphere during an experiment, otherwise the experiment 

 must fail. 



During the many trials of the apparatus in order to becomi 

 familiar with its use, and to lessen the great difficulty expe 

 rienced in maintaining the uniform difference of temperature 

 required between the interior and exterior rooms, the following 

 incident occurred, by which this difficulty was entirely ob- 

 viated. 



In the month of June, an unusual depression in the tempi 

 rature of the atmosphere had taken place during the oighl 

 season, in consequence of which the temperature "I' the exterior 

 room was found on the following morning to he 211 above that 

 of the atmosphere'. Having been previously obliged to experi- 

 ment at very high and uncomfortable temperatures, in conse- 

 quence of the heat of the weather, and presuming that llii- 

 depression would he transient, ami asnrj assistant, who attended 

 to the exterior room, was absent, no increase was made in its 

 temperature, as had formerly been dour under similar circum- 

 stances. The temperature of the interior room was elevated 

 without previous calculation, 1 5 above that of the exterior room, 

 at the period of commencement; during this operation, th< 

 thermometer in th< exterior room had not been observed, hut 

 on examination, the difference was found to he precisely 10 

 between the two rooms : considering it. however, as a fortuitous 



\ 01.. ill. — i 



