: 
, 
; 
4 
y 
4 
; 
: 
i 
W. A. Norton—Force of Effective Molecular Action. 58 
during contact pressure, correspondent to this ie ge inter- 
pre etation, was directly revealed by the experimen 
The experiments ziinded to, besides revealing ‘the laws of 
variation of the contact repulsion, showed that it was a force in 
operation beyond the range, Oc, of the effective molecular at- 
body in accordance with the indications of the molecular 
curv 
It “will robably occur to the reader that our formula and 
curve of effective eee action, afford no indication of a 
possible force of adhesive attraction, such as often manifests 
itself in the contact of aha This defect results from the 
fact that the formula involves a supposition which is not strictly 
true in cases of contact. The more comprehensive formula is: 
, 
FOES are eT eT em, dba 
dpa 2 (2r+2)? ag? 
and equation (1) is obtained by supposingn’=n. This pce! 
may not strictly exist in the contact of bodies, and n’ may be 
Pieces of plate glass in contact may be separated by the continu- 
Ous exertion of a force ever so small. 
ave now examined the general features of the typical molec- 
ular curve for solids, and shown that they represent diverse 
general mechanical properties of solids that have been experi- 
miolocats ascertained. Let us now endeavor to thera the 
tatio k for each material, and so obtain a series of definite ex- 
pressions, or corresponding molecular curves, answering to the 
Materials considered. But the value of & for a given sub- 
Stance is, from the nature of the case, incapable of direct deter- 
