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 PREFACE.

but little relation to practice. From this judgment must be excepted the admirable description by Mr. Stephenson of his locomotive engine, contributed to Tredgold's work ; but the utility of that description is diminished by the changes introduced into the locomotive engine since the time it was written, and by its own speciality, which, in the first instance, was its highest merit. The treatises of Dr. Lardner and Mr. J. Russell upon the steam engine, though most creditable performances, come scarcely under the denomination of practical works, and the same remark applies to the treatise by Pambour; so that the domain of practical detail appears to have been but little explored by engineering authors, or, if explored, the public have not profited by the research. The practical part of the present work may, therefore, be regarded as a first attempt; and the difficulty of the undertaking be consequently greater, so should the lenity be with which it is regarded.

To the leading engineers of the country my acknowledgments are due for the drawings they have furnished, and the many aids they have lent to the present undertaking. I have also to acknowledge the kind aid and encouragement afforded by Sir Robert Peel, through whose friendly offices Her Majesty's patronage was first given to the work, and through whom the permission is now conveyed for its Dedication to Her Majesty. The Artizan classes will, I am sure, appreciate these courtesies — for to them are they addressed.

JOHN BOURNE.

April 1846.

POSTSCRIPT.

The number of copies originally printed of this work having been all sold off, and a fresh supply being wanted, I have taken the opportunity of revising the stereotype plates, and introducing such corrections and improvements as were practicable under the limitations to which any change had to be restricted. The errors enumerated in the errata of the former issue have been corrected in this; and the various parts of the work now harmonise better with one another than formerly. It was my intention to have introduced something of a very practical nature about oscillating engines, screw propellers, and feathering wheels, but I found such an episode would swell into too large dimensions to be admissible, and I must now reserve what I have to say upon these topics for a supplementary work.

J. BOURNE.

193. Strand, 1st June, 1847.