S ON THE HEAT EVOLVED 



the admission of light. Every part of the room was then 

 made as tight as possible, and to furnish the room with the 

 necessary supply of air, of equal temperature, a pipe with a 

 valve was inserted through a partition into an adjoining room, 

 as its temperature was necessarily maintained very uniform, 

 for the purposes to which it was applied. Having spent nearly 

 four months of application in perfecting my apparatus, and 

 removing difficulties which presented themselves at the 

 threshold of every stage of the investigation, and feeling de- 

 sirous to avail myself cf any improvements which might he 

 suggested to me, either in the apparatus, or the intended plan 

 of conducting the experiments, I invited several gentlemen to 

 examine it for that purpose, and among them, Dr. Hare, pro- 

 fessor of chemistry in the University of Pennsylvania. 



The method which had been adopted, as described, to com- 

 ply with the last requisition, did not appear to Dr. Hare to 

 possess that degree of accuracy which was necessary, nor did 

 it equal that which every other part of the apparatus, together 

 with the intended plan of conducting the experiments, as de- 

 scribed to him, appeared to possess. Dr. Hare stated to me, 

 that, "he had long been under the impression, that no accu- 

 rate comparison could be made by means of the same single 

 room heated at different times, with different fuel, on account 

 of the varying temperature of the weather ; nor by different 

 rooms at the same time, from the difficulty of finding two 

 rooms sufficiently alike, in form, aspect, size, and materials. 

 It seemed to him indispensable, to have one room within 

 another, so that, in the interval, a uniformity of temperature 

 might be artificially sustained." As the method suggested by 

 Dr. Hare, removed this difficulty with which I had unsuccess- 

 fully contended, no time was lost in making a practical appli- 

 cation of his suggestion, and a room of smaller dimensions was 

 in consequence constructed within the room originally intend- 

 ed for my experiments, in the best manner which my archi- 

 tect could devise ; by which a free circulation of air is produced 

 on all the exterior surfaces of the interior room, and this air 

 may be sustained of a uniform temperature. 



