1893 - 94 .] on Compressibility of Fluids. 251 
But when we calculate the corresponding pressures and compare 
them with those observed, we have 
Ohs. 1 460 1250 2570 
Calc. 1 134 379 833. 
The differences between the numbers in each pair are due to the 
very rapid increase of the K term in the formula, for moderate 
diminutions of volume. The following comparison is instructive. 
The first numbers are calculated on the hypothesis that K is 
inversely as Those in the second line are the corresponding 
values of K required to make an approximate agreement between 
Amagat’s data, and the (numerical) formula above : — 
2804 3107 3462 3881 
2803 2781 2591 2144, 
Thus the requisite values of K diminish rapidly, instead of 
increasing, as the compression proceeds. In fact it would seem as 
if Van der Waals’ equation gives impossible roots in precisely that 
limited region where experiment shows that real ones are to be 
found. I intend soon to examine the cause of this strange result 
from a purely mathematical point of view. 
