152 



PROCEEDINGS OF THE AMERICAN ACADEMY 



using feet and degrees F., which becomes 429.9 in decrees C. on a 

 mercurial thermometer and in the latitude of Baltimore, compared 

 with water at 18°. 6 C. 



TABLE XXXII. — Experiments of Joule. 



The experiments of H. F. Weber* gave 428.15 in the latitude of 

 Zurich and for 1° C. on the air thermometer and at a temperature of 

 18° C. This reduced to the latitude of Baltimore eives 428.45. 



TABLE XXXIII. 



My own value at this temperature is 42G.8, which agrees almost 

 exactly with the fourth value from my own determination of the ab- 

 solute unit.f 



There can be no doubt that Joule's result is most exact, and hence 

 I have given his results twice the weight of Weber's. Weber used a 

 wire of about 14 ohms' resistance, and a small calorimeter holding only 

 250 grammes of water. This wire was apparently placed in the water 

 without any insulating coating, and yet current enough was sent through 



* Phil. Mag., 1878, 5th ser., v. 135. 



t The value of the ohm found by reversing the calculation would be .992, 

 almost exactly my value. 



