PREFACE. THIS work advances no pretensions to originality. It is what its title indicates —A Manual. The subjects, therefore, of which it treats, must more or less have been handled before, and, no doubt, more ably, fully, and clearly. The scientific and mechanical explanations, which the writer has found it necessary to give in different parts of his work, are of course little more than repetitions of definitions and principles which many treatises supply; and if, in the statement of such principles, well known terms and formulæ of expressions have been employed, it must be recollected, that the language of science is technical, and from its arbitrary precision forbids the use of any tongue but its own. The Publication of such a book may seem to require explanation, if not apology; and perhaps the best one the writer can give, will be found in the circumstances which suggested the work, and which have led to its appearance in print. In the course of a somewhat long and arduous professional career, the writer discovered, not unfrequently, considerable ignorance prevailed among Naval Cadets on points intimately connected with their duties. This may have arisen partly from their education, previous to entrance in the service, not being made to bear directly on its requirements, partly from the extensive range of information on various subjects required in a naval officer, and partly from the want of some plain works containing a good deal of instruction in short compass. As the writer has ever taken a lively interest in the improvement of young officers under his command, he was induced not only to direct their studies generally, but to assist them in those studies by a supply of papers, diagrams, and illustrations, calculated to throw some light on the subject before their minds. These papers grew upon his hands, and suggested the idea that, if collected and arranged, they might be of more extensive use to those youthful members of the profession for whose advantage they had been originally prepared; and that without the slightest intention of authorship. Under these impressions, the writer felt it his duty to place the following papers before the Lords of the Admiralty, leaving it to their judgment to decide whether they were likely to contribute towards the end desired, or whether they were only worthy of place among other well intentioned but useless writings which never see the light. Being himself entirely unambitious of the honour of authorship, and conscious that his etchings had but little claim on the favourable consideration of the public, he was contented to leave the question in the hands of his professional superiors, as an evidence, at all events, of his desire to serve a profession to which he has been all his life ardently attached. The decision of their Lordships left him no choice as to further steps. They were pleased to express a judgment that the pages laid before them were calculated to be useful, to intimate their approval of their contents, and to evince that favourable opinion in the strongest manner in their power by voting a sum of money towards the publication of the work, ordering a number of copies on their own account, and placing it on the list of books which officers are required to provide themselves with on joining the navy. This act, as liberal and encouraging on the part of the Lords of the Admiralty as it was flattering to the compilation they had been pleased to honour with their approval, necessitated its publication. The Author felt that it would be but a doubtful proof of the attachment he feels for the service to which he belongs were he from apprehension of criticism, or feelings of false delicacy, to suppress a work which his superiors have honoured with their commendation. In the handling of the several subjects the Author desires to express his obligations to those professional friends who have conferred upon him the benefit of their remarks on some points which he was permitted to bring under their personal notice.* In using certain expressions, such as "ought," "should," &c., the Author is anxious to disclaim anything approaching to a tone imperious or dictatorial. He does not affect to prescribe to any what should be the line of conduct adopted, but simply means to convey that, according to his ideas, the course or acts suggested are the proper ones to be taken under the circumstances. It will also be observed that in some chapters the ordinary style of this work has been departed from, and another more involving personal address substituted. The Author found that, in laying down directions for the performance of certain routine duties, it was more convenient and condensed to suppose himself speaking to those for whose benefit his book is intended, than to clothe these necessary directions in a style abstract and more diffuse. In fact, when duties such as the "handling" of gear came to be specified, it was found impracticable to convey directions in any other mood than the imperative. The remarks on construction are taken by permission chiefly from Mr. Fincham's " Outlines of Naval Architecture." DIRECTIONS TO THE BINDER. The two plates of Signal Flags to face page 1. The plate of Union Jack to face page 506. The eight plates of Flags to follow the Union Jack, in the order as numbered. The plates of Masts to follow those of the Flags. CONTENTS. Hydrodynamics.-Impenetrability of Matter.-Density, Volume or Bulk, Cohesion, Extension and Divisibility. — Oxygen, Nitrogen, and Hydrogen. - Carbonic Acid Gas.-Ventilation.-Composition of Water and Air. — Hydrostatic Press. - Density of Water and Hydrostatics in connection with Naval Architecture.-Displacement. ance Effect of Heat on Air. - Causes of Whirlwinds and Hurricanes. Velocity and Perpendicular Pres- sure of Winds.-Barometer.-Weight of the Atmosphere.-Prin- ciple of the Barometer. - Aneroid Barometer. - Thermometer. Table of comparative Degrees of different Thermometers.Ad- miral Fitzroy's useful Rules. - Wind and Weather Journal.-The Wet Docks.-Locks.-Dry Docks.-Angle Blocks.- Culverts.-The |