208 



PROCEEDINGS OF THE AMERICAN ACADEMY. 



TABLE VII. 



TTie Noll Data. — A contribution of much permanent value to the 

 data on thermo-electrics has recently been made by Noll,* who has 

 measured Sq e and t for thirty-two couples over a range in most cases 

 of 0° C to 218° C. The metals employed (including carbon) were 

 usually of a high and stated degree of purity, and consisted of eigh- 

 teen different substances, two of which were alloys (German silver 

 and brass) , and the remainder samples of different degrees of purity 

 or hardness of the pure substances. The couples contained, as one 

 element, for the most part, either copper or mercury. Temperatures 

 were reduced to the air thermometer scale. 



The Avenarius formula was applied to fourteen of the more impor- 

 tant of them by Noll. The deviations are given in Table VIII. 



The exponential equation I have applied to the same data. It has 

 not seemed essential to reproduce here the entire series of data, and 

 the deviations of both equations. They are, therefore, presented in a 

 somewhat more digested form. Table VIII. gives the constants for the 

 exponential equation (those for the Avenarius may be found in Noll's 

 article), the mean deviations (= data -^ equation) for each series, and 

 the mean percentage deviations (= 100 8/e). (See remark as to use 

 of e under " Barus Data.") Table IX. groups the percentage devia- 

 tions under their nearest values of t for exhibiting their systematic 



* Noll, Wied. Ann., LIII. 874 (1894). 



