38 



PROCEEDINGS OP THE AMERICAN ACADEMY 



Investigations on Light and Heat, made and published wholly or in part with appropriation 

 from the RuMFORD Fund. 



II. 



APPENDIX TO PAPER ON THE MECHANICAL EQUIV- 

 ALENT OF HEAT, CONTAINING THE COMPARISON 

 WITH DR. JOULE'S THERMOMETER. 



By H. A. Rowland. 



Presented, March, 1880. 



In the body of this paper I have given an estimate of the departure 

 of Dr. Joule's thermometer from the air thermometer, based on the 

 comparison of thermometers of similar glass. But as it seemed im- 

 portant that the classical determinations of this physicist should be 

 reduced to some exact standard, I took to England with me last 

 summer one of my standards, — Baudin, No. 6166, — and sent it to 

 Dr. Joule with a statement of the circumstances. He very kindly 

 consented to make the comparison, and I now have the results before 

 me. These confirm the estimate that I had previously made, and 

 cause our values for the equivalent to agree with great accuracy. The 

 following is the table of the comparison. 



