CONTINUOUS CALCULATING MACHINES. 
395 
engine as already described (p. 368). The recording wheel of the latter is turning at 
a rate =ydx, where, if W be the measure of the work done, 
ydx=dW 
Therefore if this wheel or roller actuate the former single sphere, the pointer of the 
movable frame of that set of sphere and rollers indicates the result 
In suitable units 
rate of working. 
— indicated HP. 
By causing the pointer in its motion to work the driving wheel of a second sphere 
whilst a clock drives the screw, the pointer indicates the ratio = a. 
Where 
dh 
dt 2 
= acceleration, or rate of change of velocity. 
So in theory any order of differential coefficient 
number of sets of spheres and rollers used. 
may be obtained, n being the 
Eig. 28. 
For integrating the volume of any irregular solid the following approximate method 
may be suggested. Let A C B, fig. 28, be the section of the solid by the coordinate 
plane parallel to which the ordinates (y) are measured. Let It Q be a screw the axis 
of which coincides with the axis of x. Suppose the pointer P to be passed round the 
solid in planes perpendicular to the above plane and at the same time carried along 
by the screw It Q—P making one revolution round the solid for one turn of P Q— 
then the final result of record of the index of roller 
