of notes of a part of the Glasgow course, drawn up for
Sir W. Thomson by John Ferguson, Esq., and printed for
the use of his students.

"We have had considerable difficulty in compiling this
treatise from the larger work-arising from the necessity for
condensation to a degree almost incompatible with the design
to omit nothing of importance: and we feel that it would

́have given us much less trouble and anxiety, and would

probably have ensured a better result, had we written the

volume anew without keeping the larger book constantly

before us. The sole justification of the course we have pur-

sued is that wherever, in the present volume, the student

may feel further information to be desirable, he will have

no difficulty in finding it in the corresponding pages of the

larger work.

"A great portion of the present volume has been in type

since the autumn of 1863, and has been printed for the use
of our classes each autumn since that date."

To this we would now only add that the whole has been
revised, and that we have endeavoured to simplify those
portions which we have found by experience to present
difficulties to our students.

The present edition has been carefully revised by Mr W.

BURNSIDE, of Pembroke College: and an Index, of which we

have recognized the necessity, has been drawn up for us by

Mr SCOTT LANG.

January, 1879.

W. THOMSON.

P. G. TAIT.

DIVISION I.

PRELIMINARY.

69

CHAPTER I.-KINEMATICS.

1. THE Science which investigates the action of Force is called, by

ERRATA.

Page 28, in diagram for first line of figures take the third.

The word Dynamometer occurring in the Index on p. 288 should
have been Ergometer, that being the term which we shall in
future use to denote this class of instruments.

translating, as it were, from Kinematics into Dynamics, and vice versa.
This is merely mentioned now in order to show the necessity for,
and the value of, the preliminary matter we are about to introduce.

6. Thus it appears that there are many properties of motion,
displacement, and deformation, which may be considered altogether
independently of force, mass, chemical constitution, elasticity, tempe-
rature, magnetism, electricity; and that the preliminary consideration
of such properties in the abstract is of very great use for Natural