320 
ANNALS NEW YORK ACADEMY OF SCIENCES 
SECTION OF ASTRONOMY, PHYSICS AND CHEMISTRY. 
November 15, 1909. 
Section met at 8:15 P. M., Vice-President Hering presiding. 
The minutes of the last meeting of the Section were read and approved. 
The following programme was then offered: 
J. P. Simmons, Lubrication and Lubricants. 
Summary of Paper. 
Mr. Simmons said: The object of all mechanisms is to control the utili¬ 
zation of energy for the performance of useful work. Owing to imperfec¬ 
tions in machinery, however, a large percentage of the energy applied is 
wasted mainly in overcoming the resistance to relative motion offered by 
moving parts. The least force applied to a perfect machine should set it in 
motion, and owing to the inertia of its parts, it should maintain a motion of 
uniform velocity, provided it performed no work. However, certain factors 
tend to prevent this, and these are first, the friction of the air, and second, 
the friction due to the rubbing surfaces. The former may be reduced to a 
minimum by the proper shaping of the moving parts and the second by the 
use of suitable lubricants. Before considering practical lubrication it might 
be well to inquire into the nature of solid friction or the friction which results 
when the surfaces of solid bodies move upon one another without the appli¬ 
cation of a lubricant. 
If two clean surfaces be pressed together considerable work has to be 
done in order that they shall move relatively to one another. Now this 
resistance which requires the expenditure of work is what we call solid 
friction, and of course this will be much less between hard and polished 
surfaces than between soft and rough. 
Illustration: Walking on ice and sandstone. Now this so-called solid 
friction is due largely to unevennesses of the moving surfaces. Absolutely 
smooth surfaces cannot be produced. 
Cohesion is another factor which requires consideration in this connection. 
This is aggravated rather than diminished by efforts to produce smooth 
surfaces. 
The lubricating value of an oil depends largely upon its viscosity or the 
resistance it offers to a shearing stress. If we consider two surfaces xx and 
yy, supposing yy to be stationary and xx to move with a uniform velocity, 
