<60 



BEPORT — 1888. 



A comparison of the corresponding columns shows that the differences, 

 except possibly in the case of A and B at the lower temperature, are 

 probably not greater than the error of experiment. It must be remem- 

 bered that A and B change by 28 bridge divisions for 1° Centigrade, 

 while for D and E the change is about 60 divisions per degree; the 

 temperature of the coils is hardly certain to 0°'l Centigrade and the 

 ■differences are within that error. As to the platinum silver coils it would 

 seem possible that F ' has risen relatively to Flat by -0001 B.A.U. and 

 that G has fallen by '00005 ; but these differences are almost too small to 

 make certain of. With regard to the results for A and B at 10° it may 

 be remarked that Fleming's line for these coils is more curved than for 

 any of the others, and that his observations at 6°'9 and at 3° lie distinctly 

 above the line which seems to represent best the observations at 0°, 9°, 

 15°, and higher temperatures. The observations are not at sufficiently 

 close intervals of temperature to enable the curved line to be drawn with 

 accuracy, and it is clear when plotting them that the curve near 10° may 

 be wrong by as much as 5 or 6 bridge wire divisions. 



We would conclude then that there is no certain evidence for a change 

 in the coils in the interval 1880 to 1888. A comparison with the results 

 of Hockin and Chrystal is not quite so easy. It is clear from the chart 

 that the coils are not exactly equal at the temperatures originally stated, 

 and any table of temperatures at which they may be said to have the value 

 of 1 B.A. Unit will depend on the assumption made as to possible 

 <;hanges in any of the coils. Chrystal in 1876 found that the coils B and 

 •C were equal at the temperatures at which they were originally stated 

 to be each 1 B.A. Unit. He supposed these coils had not altered and 

 founds on that assumption a table of standard temperatures which agrees 

 well with that of Hockin except for the coil G. According to our obser- 

 vations the coils now marked as B and C are no longer equal at the tem- 

 peratures mentioned. We find, however, that D, E, and G are practically 

 «qual at the temperatures given by Chrystal, and if we suppose G has not 

 altered we get the following table of standard temperatures : — 



Table V. 



The change in C, as shown in this table, is not large, probably hardly 

 ■greater than would be accounted for by experimental error, while D, E, 

 and G agree very closely. 



The differences in the case of A, B, and F are important. To take F 

 first. It is a platinum silver coil, No. 29 of the original report. Its 



' 'I'lie results of other experiments confirm this rise in the value of F. 



