116 G. B. Grant on a new Difference Engine. : 
opposite each wheel ae the constant ones. They consist of | 
a catch 6 and hook c. ‘ 
the teeth of the wheel and — 
. 
carries it along. The catch prices over its wheel far enouge 4 
to strike the cam on the next wheel when it gets to it, and De — 
lifted out of the teeth by it, having added to its wheel the num 
ber of spaces that the cam is distant from F. As it is 2 
up, the back catches in the nick h, and prevents it falling back — 
on the wheel, so that it moves the rest of the stroke an : 
without moving the wheel. As the carriage comes back, the 
jection on the hook strikes the rod e and the hook is lifted 
out of the catch, letting it onto the wheel again. 2 
It is n that while one wheel is being added to, the © 
next wheel should not move. For this purpose the first stroke 
adds the first, third and odd orders to the numbers on the table, 
second, fourth and even orders, the odd orders being held firm by 
a clamp not shown. Meanwhile the rod e has been moved, 
