Of the Light manifested in Combustion. 221 



of this boiler below is 8.3 inches, its depth about 

 4! inches, and its diameter above, where its neck 

 commences, is 6 inches. This boiler being placed 

 on a table, on its small wooden stand -with four 

 feet, of about fifteen inches in height, having a cir- 

 cular hole in its centre of about three inches in 

 diameter, 2000 grammes in weight of cold water (about 

 four French pounds)' were poured into it; and, its ther- 

 mometer being in its place, this apparatus was suffered 

 to remain 24 hours in a quiet room, fronting to the 

 north, to acquire the mean temperature of the place. 



At the end of that time the temperature of the 

 water in the boiler, and also of the air in the room, 

 being that of 65 F., one of my small wax tapers, 

 which had been carefully weighed, was placed afloat 

 in its small cylindrical vessel, and being lighted was 

 placed immediately under the centre of the boiler, at 

 such a distance below its bottom that the point of its 

 little flame was just on a level with the under side of 

 the perforated board on which the boiler was placed. 



The taper having burned very quietly under the 

 boiler 52 minutes and 15 seconds, the thermometer in- 

 dicating that the water had acquired 10 of heat, being 

 now at 75 F., the taper was blown out, and, after hav- 

 ing been carefully wiped till it was quite dry, it was 

 weighed a second time, when it appeared that just 

 1.52 grammes ( = 23.475 grains Troy) of wax had been 

 consumed in the experiment. 



Seventeenth Experiment. Having emptied the 

 boiler, it was filled a second time with 2000 grammes 

 of cold water; and, when the whole had acquired the 

 precise temperature of 65 F., a lighted wax candle 

 of the common size, and of a known weight, was placed 



