Pocketbook of Useful Formulæ and Memoranda
for Civil and Mechanical Engineers

vi PREFACE TO THE SEVENTH EDITION. is able to mention the names oi some to whom he is especially indebted. Mr. J. T. Hurst contributes a valuable Sup- plement. Mr. Lewis Olrick has supplied some valuable Tables. Mr. Zerah Colburn and Mr. J. Mackenzie have aided him with the results of a careful and skilful revision of the whole. The contribution of new mattei' from Messrs. Gallott and Heath, members of his staff on the Ceylon Railway, is not the least pleasing part of these acknowledgments. The Author could not with satisfaction have availed himself of these various friendly helps, without marking his sense of the public spirit and sympathy which prompted them. Guilford L. Molesworth. Colombo, Ceylon, February, 1864.