318 MR. EH. H. GRIFFITHS ON THE LATENT 
This value of 636°67 at 99°88 would become 636°60 at 100°. If we assume that 
1 gram of water gives out 100 thermal units in cooling from 100° to 0°, we get 
L = 536°60 at 100°. 
VALUES of L. 


On 100°. 
Tee Gb op oo Goo Oo 536°60 
DIETERICT .. )-) fica) Geen 596°73 a0 
GRIFriTHs (extrapolated). . 596°73 536°63 





I have learned to regard experimental coincidences with suspicion, they are so 
often misleading, but such an unusual case as the above merits attention. 
These coincidences are the more extraordinary on account of the following con- 
siderations. 
DIeTERICI assumed (ante, p. 265) as his thermal unit the “mean thermal unit” 
from 0° to 100° C. Now according to Regnautt* the ratio of the “mean thermal 
unit” to the thermal unit at 0° is as 1:005 to 1. 
If we assume Rownanp’s or Barto and Straccrati’s determinations of the 
changes below 15° (my own have not extended below that temperature) we should 
get 
“mean thermal unit” 1:005 
“thermal unit at15°” ~  -994 approximately 

au and thus Dirrerict’s value of L, if expressed in terms of the same thermal 
unit as I have used, would be increased to 603°3. 
Again, according to REGNAULT we ought to subtract 100°5 from 636°60 in order to 
obtain the value of L at 100. This would give L = 536'1. 
Some further considerations, however, tend to show that the agreement at both 
ends of the line given by my observations is not merely fortuitous. We can deduce 
the values of L resulting from my “exhaust” experiments (at any temperature 0) by 
the formula, 
O52a5 
L= 596-73 — 60106... (G,). 
Now the preliminary experiments (see Table IX., ante) although irregular, carry 
some weight and the mean of each group is in fair agreement with formula (G)). 
* “De la Chaleur Spécifique,”’ ‘ Mémoires de l’Académie des Sciences,’ tome 21. 
