4386 W. A. Norton—Force of Effective Molecular Action. 
its surface are centers of radiating impulses proportional in 
intensity to n, ane propagated according to the law of inverse 
squares. s then be proportional to the intensity of the 
radiation at Ay pois of the hemisphere, and therefore to n. 
Now the expression for the effective molecular repulsion 
(equ. 1) consists of two terms of which the first, or attractive 
term, becomes relatively very small at the molecular distances 
that obtain, at snoderate pressures, in gases (p. 346). The 
repulsive term, mart gives, then, very nearly the effective force, 
at such pressures ; and more nearly in proportion as the ratio 
pei tl smaller. Mariotte’s law should then be satisfied, for con- 
siderable variations of pressure if the term _ should vary in- 
versely as the cube of the distance («’) between the centers of 
contiguous molecules; that is, if a a If we denote by h 
the radius of the effective molecule, x’=a2+2h. As we are 
not in a position to determine a priori the law of variation of 
the size of the molecule under varying pressures, the only 
sti 
alternative is to adopt the hypothesis that os oa deduce a 
series of values of the diameter 2h, of the effective molecule 
that shall be in polo with this hypothesis, and then test 
the results and hypothesis by deducing the theoretical devia- 
tions from the law of Mariotte in special cases, and pompanng 
them with the deviations experimentally determined, Now 
find that the hypothesis that ao is satisfied by the follow- 
ing values of 2h, viz: 62° 10, 62-00, 61-26, 60°82, 58°96, 57-12, 
54°70, 51°58, 47-54, 42°24, 35° 14, 30°58, 24-74, 16:89, 2 5Ty— 
answering respectively to the following values of w (equ. 2): 
120, 115, 100, 90, 80, 70, 60, 50, 40, 30, 20, 15, 10, 5, eat 
permanen an ple nS (oxygen, aa a ooh for 
waticr 
ee should Ft have hy ie values of the ratio 
compound gases the larger values (see p. 435). We ma on 
now assume, as a basis for an approximate aan that the 
molecules of all the gases have oe diameters under equal 
