62 THE TROCHOIDED PLANE. 
passage of half a wave. 
The “trochoidal wave” may be defined as the projection of a 
right helix on to a plane parailel to its axis, and is resolvable into 
figure will be bounded on the other side by a curve of the same 
class. 
The line drawn on a uniformly moving sheet of paper, by a pen- 
dulum swinging at right angles to the line of motion of the paper, 
is also the trochoidal wave. 
connecting-rod or its continuations in the various combinations of 
the straight line, circle, and ellipse, and doubtless other figures ; 
ut each combination is reducible to the simple principle of the 
plane at right angles to the connecting-rod, moving in a circle, | 
guided by a straight line. 
The area of the triangle, that is bounded on two sides by the 
erank and connecting-rod, is directly proportional to the thrust at 
right angles to the guides: and the thrust is greatest at the centre, 
on by the trochoided plane, so that there is no violent disruption 
of any two parallel streams. 
