540 MR CLERK MAXWELL ON THE THEORY OF ROLLING CURVES. 
Ex. 3. When it is the involute of the circle, the traced curve is the spiral of 
Archimedes. 
Ex. 4. When it is a parabola, the focus traces the directrix, and the vertex 
traces the cissoid. 
Ex. 5. When it is the hyperbolic spiral, the traced curve is the tractory of the 
circle. 
Ex. 6. When it is the polar catenary, the equation of the traced curve is 
2a F r 
=f S] = reea 
r . a 
Ex. 7. When it is the curve whose equation is 
he rs) Ee ae: 
ae ee ~tog(/1 + 5-5) 
the equation of the traced curve is, 7 = @ ¢—eé-‘). 

