192 G. H. KNIBBS. 
Tt will be noticed that equation (1) expresses the observed — 
values with great precision as far as 7° or 7°5°, and that at 13-53° 
there is a sensible divergence. Since the curve for Poiseuilles 
results as far as 45° was well represented by 
f' =1 + 0:033957 + 0-00023572 
the coefficient 8 being less than half of what it is in the preceding 
equation, it is evident that the radius of curvature of the fluidity 
curve diminishes as the temperature increases. This law is 
borne out by the extension from 45° to 100° C., that is, the curve 
throughout becomes flatter as the temperature increases. Both 
Slotte’s and Thorpe and Rodger’s results shew that the second 
differences are very much smaller for the higher temperatures, 
say 50° to 100°; Slotte’s second differences are however only 
about ¢ of Thorpe and Rodger’s.! There is no satisfactory indica- 
J 
tion of any peculiarity, other than this relative rapid change of 
curvature, at the temperature of maximum density. 
6. Relative Fluidities 0° to 100° C., deduced from the efflux 
measurements of various investigators. The following table gives 
the results, deduced as explained, from the data furnished by the 
investigators whose initials are noted as follows :—P = Poiseuille, 
G=Graham, mean of tubes D and Z, R= Rosencranz, S = Slotte, 
T= Traube, N = Noack, and TR=Thorpe and Rodger. The year 
in which their observations were made is also quoted. The com- 
puted results given in the last column are obtained by formula 
(2) hereinafter given, the value at zero being taken as 100. 
Relative Fluidities 0° at 100° C. 
P. G. R. 8. T. N. 
Temp. 1846 1861 1877 1883 1886 1886 1894 puted. 
0°C.1000 1000 1000 1000 1000 1000 1000 100 
6 WNT7 16S ... Yisl* 1178" 1178 1176. 
10. 1563 1360 (<... 1872 1366. 1876 1866. 397 
_ * Values obtained by parabolic interpolation. 
a ee 
1 Can it be possible that Thorpe and Rodger’s repeated use of the one 
sample of water—flowing to and fro from bulb A to bulb B has anything 
to do with their high values of the fluidity at the higher temperatures? 
