
MR CLERK MAXWELL ON THE THEORY OF ROLLING CURVES. 521 
Let this curve roll along the curve KAS without slipping. 
Then the pole B will describe a third curve. whose pole is C. 
Let the angle DCB=9,, and CB=r;, and let 
63 = 03 (73). 

M 

We have here six unknown quantities, 6, 0, 0,7, 7,73; but we have only 
three equations given to connect them, therefore the other three must be sought 
for in the enunciation. 
But before proceeding to the investigation of these three equations, we must 
premise that the three curves will be denominated as follows :— 
The Fixed Curve, Equation, 4,=9, (7,) 
The Rolled Curve, Equation, #,=0,) (72) 
The Traced Curve, Equation, §;=¢9; (75) 
| When it is more convenient to make use of equations between rectangular 
| co-ordinates, we shall use the letters 7, 4%, a y, x;y; We shall always employ 
