STATE GEOLOGIST. DATS) 
mv" 
meg sin a= ; 
t 
The curvilinear path, therefore, conforms to the equation*™: 
COs al ey 
y=x—— — x” —— 
Sin a 2y-Sin-a 
s ast? ® ‘ 
ci ce N 
reyes Sf 
ZINN AA 
Salva y 
i) 
Fig. 44. Diagram illustrating action oH SUIDE mill, after Fischer. 
In the accompanying figure this path is the line AA,A,. The vertical 
velocity has negative acceleration, becomes zero at A, and hence the 
pebbles appneacin cach othem. touching at =A.) “ihe charae as thus 
forced aside at this point and the path must differ from the theoret- 
ical curve owing to the collision of the pebbles. After reaching A the 
pebbles follow the curve with accelerated velocity, and hence the intervals 
between them become larger. A second layer of pebbles begins its curvi- 
imearepatimat 13, a tnd at ©, etc. Mnese curves are bound to be less 
clearly defined, but they frequently separate from each other so markedly 
that it is possible to see through between them. Most of the grinding 
effect is thus produced at A,, where the motion of the particles to be ground 
is the resultant of the vertical velocity and the forward motion. A pound- 
ing and rubbing action is thus exerted. 
The grinding effect depends then on the vertical distance of the 
drop, the velocity of the drum and weight and number of the pebbles. 
*In figure 44 the angle,a, of the formula is indicated by the Greek letter Psi. 
