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MINUTES OF PROCEEDINGS OF 
Another advantage gained is that perfect accuracy in finding the 
centre of gravity of the whole mass is not required. As long as it is 
anywhere inside the circumference of the small circle whose involute is 
taken, there will be no dead point in the motion of the elevators. 
This margin of permissible error is of much practical utility. 
It will be observed that these remarks do not apply to that part of 
the elevator which is meant to give the counterweight a rapidly in¬ 
creasing advantage over the gun, and so to subdue the recoil. 
The tracing represents a Moncrieff carriage for a 32 converted 
64-pr. gun. In it, L represents the small circle whose centre is oppo¬ 
site the common centre of gravity, and from which the arc o.f the 
involute is unwound. The marks on the outer side of the elevator 
correspond to the small marks on the circle, and shew the successive 
positions of the line in tracing the involute. 
The problem solved may be thus stated:—In what form should a 
uniformly loaded rocker be cut that one end should have a constant 
moment over the other ? The required form is that of an involute of a 
circle whose centre is the centre of gravity of the whole mass. 
