is required of the propeller is to push her forward. If set so as to act
in a direct line with the plane of motion, it will use all its force to
push her forward; if set so as to use its force in a perpendicular
direction, it will use all its force to raise her out of the water. If
placed at an angle of 45° with the plane of motion, half the force will
be used in raising the ship out of the water, and only half will be left
to push her forward.

ENOS M. RICKER.

Park Rapids, Minn., Jan. 23, 1886.

* * * * *




SIBLEY COLLEGE LECTURES.

BY THE CORNELL UNIVERSITY NON-RESIDENT LECTURERS IN MECHANICAL
ENGINEERING.




PRINCIPLES AND METHODS OF BALANCING FORCES DEVELOPED IN MOVING BODIES.

BY CHAS. T. PORTER.

INTRODUCTION.