490 
MR. E. H. GRIFFITHS ON THE VALUE OF 
Table XLV.—Comparative values of J given by Joule, Rowland, and Griffiths. 
Date. 
Joule’s method. 
Tempera¬ 
ture of 
water. 
Joule’s value 
in the 
metric system. 
Reduced to 
Rowland’s air- 
thermometer. 
Rowland, 
1880. ! 
Griffiths, 
1892. 
1847 
Friction of water . 
o C. 
15 
442-8 
427-4 ! 
427-9 
1850 
• • • 
14 
426-8 
427-7 i 
428-1 
1850 
Friction of mercury . 
9 
427-5 
428-8 
428-6 
1850 
99 99 • • 
9 
428-7 
428-8 
428-6 
1850 
Friction of iron.... 
9 
429-1 
428-8 
428-6 
1850 
99 99 • • • • 
9 
428-0 
428-8 
428-6 
1867 
Electric heating 
18-6 
428-0* 
426-7 
427-6 
1878 
Friction of water . 
14-7 
425-8 
427-6 
427-9 
1878 
99 S9 • • • 
12-7 
427-1 
428-0 
428-2 , 
1878 
9 9 9 '> • • * 
15-5 
426-0 
427-3 
427-9 
1878 
14-5 
422-7 
427-5 
428-0 
1878 
99 99 • * • 
17-3 
426-3 
426-9 
427-7 
Rowland remarks as follows : “Joule rejected quite a number of his results, but 
I have thought it best to include them, giving them small weight however. In this 
way we obtain a value of Joule’s experiments of 426’75 at 14°’6 C., my value at 
this point being 427*52 ; the difference amounts to 1 in 550 only,” 
Adopting this method of comparison we get (at 14°*6 C., and expressed in kilo- 
grammetres at Baltimore): 
Joule, Rowland, Griffiths, 
426*75 427*52 427*98 
Thus our difference from Joule amounts to 1 in 350,t and our difference from 
Rowland amounts to 1 in 930.| 
The difference between Rowland’s determinations of the changes in the specific 
heat of water and ours, would cause the values of J to be identical if expressed in 
terms of a thermal unit at 11°*5 C., and below that temperature Rowland’s value 
would be the greater, 
[Notes by E, H, G,, added April, 1893, 
1, No change in the value of the various units, or constants, involved in our 
* Value deduced by Rowland by assuming bis own value of the obm. 
f If we attach equal weight to the different values given by Joule (Rowland in obtaining the above 
numbers attached ai’bitrary values to different experiments and methods) wm obtain J = 42S'23 as the 
mean value at 13°'2 0., i.e., J = 428'08 at 14°'6 C. This exceeds our value by 1 in 4281. 
t If we assume the E.M.F. of our cells to be that of the Cavendish standard, our value would be 
427'86 and these diffei’ences would become 1 in 386 and 1 in 1260 respectively. 
