"If those who are occupied in the proper business concerns of life, and its severest toils, had really
No time for study, then would the great mass of society be doomed to perpetual mental degradation;
but every man can spare at least one hour in the twenty-four to the improvement of his mind; and
one hour a day is about equal to four entire years in every twenty; which, so far as time is concerned,
is sufficient to complete as extensive and varied a course of study as can be pursued from entering
to leaving college. With this one hour at his command, each man has the principle of freedom in
his own bosom; and will be a nobleman and gentleman—a scholar and a philosopher, though he tol
at the desk or in the shop, or in the field, for his daily livelihood."-The Freedom of the Mind.

London:

PUBLISHED BY M. SALMON,

MECHANICS MAGAZINE office,

115, FLEET STREET.

M.DCCC.XXX.

PREFACE

TO

THE THIRTEENTH VOLUME.

A JOURNAL which, like the "MECHANICS' MAGAZINE," consists principally of the spontaneous contributions of a particular class of readers, will always possess the peculiar merit of reflecting with great vividness the impressions which are uppermost in the minds of that class. Whatever concerns or interests them most, for the time, is sure to be more fully treated of there, than any where else. Were any one asked, 'What are the subjects which, during the past year, have most occupied the attention of scientific men?' he would doubtless answer'Railways and Steam-carriages.' And, on referring to this new Volume of our Work, it will be seen that Railways and Steam-carriages form, accordingly, its leading themes. It may, with great safety, be asserted, that in no other Journal of the day, is there to be found so much valuable information on these all-engrossing topics, or so many helps to the progress of improvement in the application of steam power to locomotive purposes.

The other matters, of which the present Volume is made up, will be found distinguished by the same features of variety and usefulness which have characterised the "MECHANICS' MAGAZINE" from its commencement. Almost every branch of knowledge, and every walk of life,

302175

has contributed something original to the fund of information and amusement here collected.

On the General Principles of Physics, there are some Essays by Mr. Hopwood, not more remarkable for the great clearness of their style, than for the new and (we apprehend) sound views they contain.

To the elucidation of Practical Mechanics, Mr. Davy and Mr. Baddeley have, as usual, contributed largely; so also have Mr. Harrison and S. Y., even in the midst of a fierceness of controversy, not very favourable to the interests of truth. For many valuable communications to the same department, we are indebted to Mr. Cheverton, Mr. Saul, Henry D., Miliwal Thingk, a Country Curate, S. P. B., B. S., and other occasional Correspondents.

The New Inventions brought into notice are numerous, and some of them of great promise; we may mention, in particular, the Perpetual Lever of Mr. Franks (p. 366); the Buhlcutting Machinery of Mr. M'Duff (pp. 129, 287); Mr. Lacey's Apparatus for Suspending Carriage-bodies (p. 274); Messrs. Braithwaite and Ericsson's Method of Manufacturing Salt (p. 418); Jenour's Brittle Charges, p. 419; and Long's Wooden Frame Bridges (p. 434).

The department of Mathematical Inquiry continues, with the aid of O. C. F., Mr. Woollgar, G. S., Mr. Utting, Mr. Jopling, R. C. jun., Mr. Hubert, Mr. Hughes, Amicus, and other learned contributors, to be sustained with a degree of ability which has given the "MECHANICS' MAGAZINE" a place, second to none, among the publications devoted to this branch of knowledge. The present Volume contains the new set of Logarithmic Tables, by Mr. Woollgar, which we announced in the Preface to our last Volume. They are the most concise, we believe, ever published, yet com