36 



EEPORTS ON THE STATE OF SCIENCE. 



In practice two manganiii coils act as intermediaries. The measured 

 values in 1903 and 1907 are given in the following table : — 



Table I. 

 Givinff the Values of the Mercury Standards in 1903 and 1907. 



With the exception of P the relative values of the standards have kept 

 remarkably constant, and in the case of P the increase in resistance may- 

 be apparent only, for only in 1907 has an increase been noted. It is 

 thought that a very thin film of grease may be coating a portion of the 

 inner wall of the tube. As the tubes M, G, and S are of French verre 

 dur, and the remainder of Jena 16'" glass, there is justification for 

 assuming the constancy of the standards. It is of interest to state that 

 the relative values of the French mei'cury standards in 1885 and 1905, and 

 of the mercury standards of the Reichsanstalt in 1893 and 1904, are also 

 in very good agreement. 



Wire Standards of Platinum, Platiauni- Iridium, Gold-Silver, and 



Platinum,-Silver. 



The original coils of the Association are six in number : two are of 

 platinum, two of platinum-iridium, one of gold-silver, and one of platinum- 

 silver. They were compared together by Messrs. Matthiessen and Hockin 

 in 1865-G7, by Messrs. Chrystal and Saunder in 1876, by Dr. Fleming in 

 1879-81, by Dr. Glazebrook and Mr. Fitzpatrick in 1887-88, and by the 

 author in 1908. In addition to these six coils, Messrs. Chrystal and 

 Saunder examined a platinum-silver coil marked No. 29 F, and also a coil 

 known as Flat, while measui-ements of another platinum-silver coil H are 

 given in the Report for 1888. These coils— in all, 9 — have remained in 

 charge of the Secretary. 



In a report to the Association in 1888 Dr. Glazebrook discussed the 

 probable changes which had taken place in the coils since 1867, and 

 changes in the platinum-silver coils only are discussed in the Reports for 

 1892 and 1903. In 1865-67 the probable error of the comparisons appears 

 to have been of that order which would be introduced by an error in the 

 temperature of the coils of about 0°'l C. In 1888 and 1903 the error of 

 the comparisons corr responds with an error in the temperature of the coils of 

 !i little less than 0°'l C, and in 1908 the error has been i-educed so as to 



