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uniform rotation of the cones. A‘ cam might be made to act 
upon the common axis so as to slide it in or out according to 
any given law, and so produce any required motion in the pulley 
A, There are endless varieties of uses to which this device 
might be applied. It was originally designed in order to reduce 
the rapid rotatory motion of a circular saw into a slow recti- 
linear motion in order to bring the timber up to the saw, in 
such a way that the advance might be instantly stopped or 
reversed, or might be made slower to suit the nature of the 
timber employed. Some such contrivance might possibly be 
useful for ploughing purposes, so as to enable lighter tackle to be 
used than at present, and to regulate the speed of the plough 
according to the nature of the ground. 
Prof. CAYLEY asked whether the third machine could be 
made accurate enough to allow it to be applied to the work of 
a pentagraph, for theoretically it was capable of it. 
Monpbay, Feb. 12, 1872. 
THE PRESIDENT (PROFESSOR HUMPHRY) in the Chair. 
It was announced by the President that the Adjudicators 
of the Hopkins Prize (Professors Stokes, Tait, and Clifton) had 
awarded it to Professor J. Clerk Maxwell. 
It was also announced that Vol. XI. Part 3 of the Society’s 
Transactions was now ready, and would be delivered to the 
members on application. 
Communications were made to the Society: 
(1) Further observations on the state of an eye affected 
with a peculiar malformation. By tHe AsrTrRo- 
NOMER Royat. 
