ON STANDARDS FOR USE IN ELECTRICAL MEASUREMENTS. 99 
with some care. A change in F had been noted ina postscript to the 
Report for 1888. The general conclusions of that Report were that up 
to the summer of 1888 there had been no change in the value of the coils. 
It was shown that all the original platinum silver coils examined then— 
those of Messrs. Elliott, H. A. Taylor, aud others, as well as those belong- 
ing to the Committee—had apparently fallen in value relatively to the 
mean B.A. unit by about :0007 B.A.U. since 1867, but evidence was 
adduced to show that the fall was only apparent, due to an error in the 
temperature coefficient used at that date. A single observation of 
Chrystal in 1876 pointed to the possibility of a change in F, but that 
change was not confirmed by other evidence ; while so far as the platinum 
silver coils were concerned, the observations of Dr. Fleming in 1881, and 
_ myself in 1888, agreed closely. 
Since 1888, however, changes have shown themselves. 
These are evidenced by the three following tables II., III., and IV., 
which give the differences Flat—F, Flat—G and Flat—H respectively. 
Taste Il.—Value of Flat—F. 
Date Temperature Value 
i 10:0 105 
Chart 1888 5 : ; 15-0 9:5 
1 20:0 85 
May 16,1888 . ; F : 14°8 9-0 
PME 2s) oy é : 5 0-0 30 
BUCY Sy rn g5 os 5 e ; 14°8 3°8 
Pedy 13, 5 . « . 2 : 14:2 4-2 
mouly 13, 5 . ; : : 14:6 33 | 
ialyela, 450° : : 14:7 3°3 
iv 7 ar : - = 16°7 4:2 
Jan. 1890 . : : 5 10:0 -4£:0 
May TE ‘ F : 14:4 ashy 
Aug. as ; 3 ‘ 5 16:9 -3°2 
| Aug. ‘gc 5 5 ; 16°7 -3°0 
Taste IIl.—Value of Flat—G. 
Temperature Value 
10:0 175 
15:0 18-0 
20:0 18°5 
14:6 16°6 
10:0 16°9 
45 16-7 
6:0 16°6 
14:4 21°5 
16:0 21-4 
16:0 22:2 
16:0 22-2 
16:0 22:2 
19-0 21:8 
17:0 22:3 
16°5 22°6 
16°5 22°5 
