A Manual for Naval Cadets - John McNeill Boyd

This historic book may have numerous typos and missing text. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1860 Excerpt: ...ships. From what has been said, it is to be hoped that the reader will have little difficulty in comprehending the principles which govern the different manoeuvres executed on board a ship, such as Tacking and Wearing. But he must bear in mind that these manoeuvres are not entirely carried out by means of the sails, but that the rudder plays the most important part. Now the action of the rudder is dependent on the speed with which the ship passes through the water, and this again upon the power of the sails. The example of the Lever must therefore be followed with some limitation. In Wearing, for instance, while we to a certain extent neutralise the after sail, it is desirable to keep such an amount of sail in full action as to keep up the speed of the ship. This is done by not only keeping the head sails full but the main top-sail also, or very slightly lifting, the mizen top-sail and driver alone being neutralised. Again, in tacking under ordinary circumstances, so much advantage is derived from keeping way on the ship to the last moment before the sails shake, that none of the head sails are neutralised at all. CHAP. XIX. MEASURES AND WEIGHTS. The earliest mark of time with which man could have been acquainted, must have been the successions of light and darkness, or the division of a certain portion of time into day and night. After that, .the observation of the movements of the heavenly bodies, the length and direction of shadows, the rise and fall of tides, the escape of water from vessels, and the consequent subsidence of the fluid within--would all suggest themselves as so many means of marking the rate at which time was passing. The sun-dial of Ahaz, the clepsydra, the sand-glass of the Greeks, the notched candle of the Saxons, were all inventions, ..