HENRY MOSELEY, M.A. F.R.S.

CHAPLAIN IN ORDINARY TO THE QUEEN, CANON OF BRISTOL, VICAR OF OLVESTON;

CORRESPONDING MEMBER OF THE INSTITUTE OF FRANCE, AND FORMERLY PROFESSOR

OF NATURAL PHILOSOPHY AND ASTRONOMY IN KING'S COLLEGE, LONDON.

In the Clerk's Office of the District Court of the United States, for the Southern District

of New York.

W. H. TINSON, Stereotyper.

R. CRAIGHEAD, Printer.

APR 10 1922

EDITOR'S PREFACE.

THE high place that Professor Moseley occupies in the scientific world, as an original investigator, and the clearness and elegance of the methods he has employed in this work have made it a standard text book on the subjects it treats of. In undertaking its revision for the press, at the request of the publishers of this edition, it has been deemed advisable, in view of the class of students into whose hands it may fall, to make some slight addition to the original. This has been done in the way of Notes thrown into an Appendix, the matter of which has been gathered from various authorities; but chiefly from notes taken by the editor, whilst a pupil at the French military school at Metz, of lectures delivered by General Poncelet, at that time, 1829, professor in that school. It is a source of great pleasure to the editor to have this opportunity of publicly acknowledging his obligations to the teachings of this eminent savan, who is distinguished not more for his high scientific attainment, and the advancement he has given to mechanical science, than for having brought these to minister to the wants of the industrial classes, the intelligent success of whose operations depends so much upon mechanical science, by presenting it in a form to render it attainable by the most ordinary capacities.

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The editor would remark that he has carefully refrained from making any alterations in the text revised, except corrections of typographical errors, and in one instance where, from a repetition of apparently one of these, he apprehended some difficulty might be offered to the student if allowed to remain exactly as printed in the original.

UNITED STATES MILITARY ACADEMY,

West Point March 8, 1856.

PREFACE TO THE SECOND EDITION.

I HAVE added in this Edition articles :-first, "On the Dynamical Stability of Floating Bodies;" secondly, "On the Rolling of a Cylinder;" thirdly, "On the descent of a body upon an inclined plane, when subjected to variations of temperature, which would otherwise rest upon it;" fourthly, "On the state bordering upon motion of a body moveable about a cylindrical axis of finite dimensions, when acted upon by any number of pressures.”

The conditions of the dynamical stability of floating bodies include those of the rolling and pitching motion of ships. The discussion of the rolling motion of a cylinder includes that of the rocking motion to which a locomotive engine is subject, when its driving wheels are falsely balanced, and that of the slip of the wheel due to the same The descent of a body upon an inclined plane when subjected to variations in temperature, which otherwise would rest upon it, appears to explain satisfactorily the descent of glaciers.

cause.

The numerous corrections made in the text, I owe chiefly to my old pupils at King's College, to whom the lectures of which it contains the substance, were addressed. For

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