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Engin. Librar

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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