350 



Mr. R. T. Grlazebrook's Comparison of 



Thus there is a difference of '0005 legal ohm between the 

 two. My results are based upon the value of the resistance 

 of mercury in terms of the B.A. unit adopted by the British- 

 Association Committee. If we denote by M the resistance at 

 0° C. of a column of mercury 1 metre long, 1 square millim. in 

 section, then, according to the number adopted by the Com- 

 mittee, M# _ .9540 B.A.U. 

 B.A.U. = 1-04820 M. 



The most recent values actually found for these relations 

 are given below: — 



Table V. 



M in B.A.U. 



B.A.U. in M. 



Observer. 



•95412 



•95374 



•95334 

 •95411 



1-04808 { 



1-04851 | 



1-04894 

 1-04809 



Rayleigh* and 

 Sidgwick. 



Mascartt,Nerville, 

 and Benoit. 



Strecker J. 



L. Lorentz §. 



M. Benoit has not compared his tubes directly with the 

 B. A. units. The mean of my comparisons gives for his 

 mercury tubes, m. = -95348 B.A.U. 



B.A.U. = 1-04878 M. 

 Thus there is a difference of -0005 ohm between standards 

 issued by M. Benoit as representing the legal ohm, and those 

 issued by myself on behalf of the B. A. Committee, M. 

 Benoit's standards being less than mine by that amount. 



Some other points remain to be noticed. The first time 

 that I filled Eos. 37 and 39, I obtained results for the resist- 

 ances differing appreciably from those given above. They 

 were filled each time with equal care, the mercury had been 

 treated in the same manner, and there seemed no reason, 

 taking each observation separately, why one should be better 

 than the other. For No. 37 I found on April 8th the value 

 1*00044 legal ohms ; I noticed on April 9 that this had gone 

 up to 1*00071 ; and on passing the mercury through as already 

 described, it rose further to 1*00080. These differences are 

 considerably greater than any possible errors of observation ; 



* " On the Specific Resistance of Mercury/' Phil. Trans, pt. 1, 1883. 



f Journal de Physique, June 1884. 



X Abh. der buyer. Akad. Bd. xv. ; also Wied. Ann. vol. xxv. 



§ Wied. Ann. vol. xxv. 



