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PRINCIPLES

OF

MECHANISM,

DESIGNED FOR THE USE OF STUDENTS

IN THE UNIVERSITIES,

AND FOR

ENGINEERING STUDENTS GENERALLY.

BY

ROBERT WILLIS, M. A., F.R.S., &c.

JACKSONIAN PROFESSOR OF NATURAL AND EXPERIMENTAL PHILOSOPHY

IN THE UNIVERSITY OF CAMBRIDGE.

LONDON:
JOHN W. PARKER, WEST STRAND.

CAMBRIDGE: J. & J. J. DEIGHTON.

M.DCCC. XLI.

CAMBRIDGE:

PRINTED AT THE UNIVERSITY PRESS.

PREFACE.

In the present work I have employed the term Mechanism as applying to combinations of machinery solely when considered as governing the relations of motion. Machinery as a modifier of force, has in the science of Mechanics occupied the attention of nearly every mathematician of eminence who has arisen in the world; but, by some strange chance, very few have attempted to give a scientific form to the attractive and valuable results of mechanism ; for it cannot be said that the few and simple machines which form the examples in books of mechanics, are to be regarded as even forming a foundation for the principles upon which is to be based a science that will enable us either to reduce the movements and actions of a complex engine to system, or to give answers to the questions that naturally arise upon considering such engines ;-for example, are the means by which the results are obtained the best that might have been employed ? or what are the various methods that might have been substituted for them ? Yet there appears no reason why the construction of a machine for a given purpose should not, like any usual problem, be so reduced to the dominion of the mathematician, as to enable him to obtain, by direct

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