176 
DR. H. T. BARNES ON THE CAPACITY FOR HEAT OF WATER 
from which 
therefore 
R/S 2 — Sj/R = 2 (r -f dr) = p (d ?j — d x ), 
2clr 
(d, — d x ) - {d x — d. 2 ) ’ 
dr (d x -d,) 
{d s - dp - (d x - d,) ’ 
the value of dr being ( S — ^)• 
& \ S + 100/ 
This gives for R the value S(1 + r), where S is the known standard. The value 
of p was obtained a number of times, both by myself and a number of the students. 
The values obtained since 1897 are in ohms—'001022, '001015, '001019, '001011, 
•001028, '001028. 
This gives a mean value of '001020 ohm per division for bridge-wire C. 
The following is a list of the standard 1-ohm coils used in the comparisons. Each 
coil had a certificate signed by the secretary of the Electrical Standards Committee, 
and dated either in 1892 or 1893. 
List of Certified Standards. 
Platinum-silver Wire Coils (embedded in Paraffin Wax). 
O 
No. 3565 certificate, '99957 true ohm at 16'4. 
„ 3566 
„ '99960 
55 
16-5. 
„ 3567 
„ '99949 
55 
16-4. 
„ 3568 
„ '99961 
55 
16-5. 
„ 3569 
„ '99964 
55 
16-5. 
„ 3402 
„ '99971 
55 
16-7. 
„ 3403 
„ '99967 
55 
16-5. 
„ 3404 
„ '99970 
55 
16-7. 
„ 3405 
„ -99960 
55 
16-3. 
„ 3406 
„ -99960 
5 5 
16-3. 
Manganin Wire Coil (in Oil-bath). 
O 
No. 4086 certificate, '99978 true ohm at 15'9. 
Reichsanstalt Standard. 
No, 1214 marked 1 true ohm at 20° C, 
