448 
MR. E. H. GRIFFITHS ON THE VALUE OF 
Table XXII. 
Date. 
Exp. 
Range E^. 
Range 
C. 
Mean 
tempe¬ 
rature 
and 
tempe¬ 
rature of 
outer 
batli. 
Time. 
Rate. 
Range ^ ^. 
-n-- - X 10®. 
iime 
(Rate 
correc¬ 
tion) 
X 106. 
1 
i 
(Eise pet 
second at 
rate 30) i 
X 106. ; 
Aug. 12, 1892 
LY. 
87'5-108-5 
•509 
14-251 
1009-2 
29-99 
504 
-H 1 
505 
LVI. 
394-5-409-5 
•389 
21-873 
802-7 
29 80 
485 
+ 10 
495 
n 
LYII. 
494-5-503-5 
•241 
24-433 
470-9 
30-21 
512 
-11 
501 
As we regarded these experiments only as preliminary, they were somewhat 
hurriedly performed, and we proposed investigating this point more fully later on. 
It has been previously pointed out (p. 440) that, in any case, the conclusions arrived 
at would not affect our results, and we only give them to show that no marked 
change is indicated. Some similar exjDeriments performed in 1891 had led to the 
same conclusion. 
During this year’s (1892) experiments we were not troubled by any air, or water, 
leakages into the annular space between the calorimeter and the steel chamber. A 
great portion of our time and attention in previous years having been devoted to 
leak-hunting, we had considerable (unwished for) opportunities of investigating the 
effects of changes of pressure, or alterations in the dryness of the surrounding 
medium. 
The smallest trace of moisture has a most astonishing effect on the radiation 
coefficient. The change in the rate of rise is most marked, and if the moisture 
present is sufficient to saturate the space when the calorimeter is cooled down, aU 
attempts to obtain a radiation coefficient are hopeless. Any trace of aqueous vapour 
could immediately be detected by its effect on the rate of rise, and on one or two 
occasions was sufficient to prevent any rise whatever. 
Considerable effect was also caused by changes in pressure, and when comparing 
the results obtained from different masses it must be remembered that the pressure 
was frequently changed. Although we were then not conscious of the full import¬ 
ance of this point, we endeavoured to maintain the pressure unaltered from the time 
that any set. of stirring determinations were made until the corresponding J experi¬ 
ments were completed. 
