Thermo-electric Interpolation Formula. 475 



statement was given to indicate the reliability of the stated 

 percentage composition of the various alloys used. For when 

 closely examined, the data seem to indicate a definite relation 

 between the composition and the E.M.F., as was shown by a 

 relation discovered between the constants in my exponential 

 equations for the various alloys. The deviations were only 

 such as might be attributed to uncertainty of composition, 

 but as no measure of the latter was given, a statement of 

 the relations and interesting inferences from them is not 

 warranted. It is also unfortunate that an analysis, or at 

 least a definite statement of the percentage purity, was not 

 given for the gold, copper, and silver whose melting-points 

 were observed. The assertion that the gold showed on 

 qualitative analysis only a trace (" Spur ") of copper, and the 

 silver a "trace" of iron, is hardly definite. The value of the 

 whole work would have been enhanced by these additions far 

 more than in proportion to the comparatively small labour 

 demanded by them, and such completeness is naturally to be 

 expected in work emanating from this source. It is to be 

 hoped that a continuation of this research is in progress, and 

 that additional high melting-points may be measured. 



Table III., columns 1 and 2, quotes the interpolated 

 mean values of several comparisons expressed in international 

 microvolts and degrees centigrade. With regard to these 

 data it should be stated that below about 400° they were not 

 supposed to be of as high accuracy as above that point. Also, 

 that owing to unavoidable circumstances the data below 300° 

 were obtained with only a single air-thermometer bulb, and 

 similarly those above about 1300° with one bulb only, but a 

 different one, while the data intermediate between 400° and 

 1300° are the mean of observations with the two bulbs. This 

 fact may partially account for the erratic character of the 

 residuals above 1300°, where the deviations are so great and 

 so distributed (see diagram, page 483) as to render these 

 observations of very little service. Direct comparison with 

 the air-thermometer was made with one 10 per cent rhodo- 

 platinum couple " A " only. 



The parabolic formula applied to these by flolborn and 

 Wien, when corrected as to decimal points *, is 



^ = l-376.10- 1 (2o6)-4-841.10- 6 (^^) 2 + l-378.10- 10 (2^) 3 . 

 Range - 80° C. to +1445° C. 

 The residuals are given in Table III., columns 3 and 4. 



* The equation at both references, and stated to be in microvolts and 

 degrees, is erroneously printed as 



«^=/(e) = 13-76e-0-004841e 2 +0'000001378e 3 ." 



