218 



Mr. J. Joly. 



Observations, &c. (continued). 



San Feraando : — Instituto y Observatorio de Marina. Anales (Ob- 

 servaciones Meteorologicas). Aho 1888. 4to. San Fernanda 

 1889. The Observatory. 



"On the Steam Calorimeter." By J. Joly, M.A., B.E., 

 Assistant to the Professor of Civil Engineering, Trinity- 

 College, Dublin. Communicated by Professor Fitzgerald, 

 M.A., F.R.S., F.T.C.D. Received November 26,— Read 

 December 19, 1889. 



[Plates 6, 7.] 



In two papers read before the Royal Society,* some three years 

 ago, I described a "Method of Condensation" in calorinietry. A 

 number of experiments in support of the reliability of the new 

 method are contained in those papers, as well as a description of snch 

 forms of apparatus as I had then been using. The apparatus, 

 however, could not be said to be the result of a very prolonged 

 study of the capabilities of the method, and possessed many defects, 

 chiefly on the score of convenience in effecting the measurements. 

 A continued use of the method since that time and its application to 

 some exacting measurements have led to various alterations in the 

 apparatus, so that, after many reconstructions, entirely new forms 

 have been conferred on the instrument. I purpose to describe two 

 new forms : a single calorimeter similar in type to the older instru- 

 ment, but differing in construction ; and a differential calorimeter, 

 rendering possible measurements which could hardly be effected in 

 the single type of instrument.. 



In the interval, too, a wider knowledge of the capabilities of the 

 method has been acquired. Its errors have been enquired into. On 

 the question of the errors arising from radiation many hundreds of 

 experiments have been made. The general results of these will be 

 found in the following pages. Again, I have from time to time tabu- 

 lated such data as are of use in the applications of this calori- 

 metrical method. These I ask permission to include, so as to render 

 this account of the method as complete as it can, within convenient 

 bounds, be made. As, however, descriptions of the principles of the 

 method, and of many experimental tests to which it has been sub- 

 jected, are accessible both in Professor Bunsen's paperf on the 



* " On the Method of Condensation in Calorimetry " and " On the Specific Heats 

 of Minerals," 1 Boy. Soc. Proc.,' vol. 41, p. 352 et seq. 



f " Uber daa Dampf calorimeter," Wiedemann's ' Annalen der Physik und Chemie,' 

 vol. 31, 1887, p. 1. 



