34 



SIXTH REPORT — 1836. 



do the numbers in question correctly represent the specific heats of 

 the different gases under equal volumes, as given by his experiments ; 

 for being unaware of the omission just alluded to, he had erroneously 

 applied to his direct results the correction for the per centage of air as- 

 certained by analysis to be present in each gas. The formula, in fact, 

 for this correction was contrived for the case of specific heats under 

 equal weights, instead of, as it should have been, that of specific heats 

 under equal volumes. When this correction is properly made, the ori- 

 ginal numbers undergo material modification, as maj^ be seen by in- 

 spection of the following table. The original numbers are in column 

 2, and the corrected ones in column 3. 



Upon these results. Dr. Apjohn stated that he never placed much 

 reliance. The apparatus employed was very imperfect, particulaily in 

 not permitting more than a single experiment with the same quantity 

 of gas ; and he also saw reason to doubt that he had, in every instance, 

 by means of it accomplished perfect desiccation. Under these circum- 

 stances he had always contemplated returning to the investigation, 

 and towards the latter end of last July he did, in fact, commence 

 a fresh series of experiments, which were conducted on the following 

 plan. 



A pair of copper gasometers with glass bells, such as are usually 

 employed by chemical lecturers, were charged with a proper quantity 

 of oil of vitriol instead of water, and placed upon a table, at the di- 

 stance of three feet from each other, the brass rods attached to tlie bells 

 being susjiended to the extremities of a stout cord passing over a pair 

 of runners fixed in the ceiling of the laboratory. Between the lower 

 stop-cocks a couple of glass tubes were interposed, connected to the 

 stop-cocks by caoutchouc collars, and fitting at their other extremities 

 to each other by a tight ground joint. In the longer of these tubes the 

 dry thermometer was permanently placed, and into it also the wet one 

 was introduced previous to the commencement of an experiment. 

 Matters being, we shall suppose, thus prepared, and the unimmer- 

 sed bell occupied, — first with atmospherical air, — deprived by the oil of 

 vitriol of its moisture, pressure was made upon it by an assistant so as to 

 force its contents in a rapid current into the second bell, through the 

 tube containing the wet and dry thermometers. During this operation 



