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PUBLISHER OF CHARTS AND NAUTICAL WORKS,
157, LEADENHALL STREET, E.C.
THE first part of this work (pp. 1-80) has been written to give, in as plain terms as possible, a complete knowledge of the intent and purpose of Practical Navigation-to show the Yachtsman how to work up a Day's Work and to keep a Ship's Reckoning, how to find a Ship's Place at Sea, whether by Dead Reckoning by Observation of the heavenly bodies, and how to use and turn to good account the various Instruments required for the safe conduct of a vessel across the ocean,-not forgetting the Deviation of the Compass; while instructing him on these subjects, it has not been lost sight of that he may wish to obtain the Board of Trade Yachting Certificate, and therefore various Examination Papers (with explanatory notes) have been inserted in their proper place.
Appended to this part will be found Brief Rules in Navigation to assist the Yachtsman in working the questions set at the Board of Trade Examination. Then follow the International Code of Signals, Rule of the Road, &c., finishing with notes on Seamanship, in question and answer.
LONDON, May, 1877.
W. H. ROSSER.
Adjustments of the Sextant (Examination Paper)
To Read the Sextant
Tides and Time of High Water
Magnetism of Iron Ships
Deviation of the Compass (Examination Paper)
YOUNG SEAMEN AND YACHTSMEN.
Navigation has been defined as the art of conducting-in the sense of piloting or guiding-a ship from one port to another; and this piloting on-the open ocean, far out of sight of beacons, landmarks and lighthouses, rests on the determination of DIRECTION, DISTANCE, and RELATIVE POSITION,-combining observation with calculations that are the practical application of Geometry and Astronomy. It is the purpose of this little work to explain the use of the instruments, and the kind of calculations, that are required in Navigation, as well as the usual methods that are adopted from day to day during a voyage to find what is called the SHIP'S PLACE AT SEA, which is the basis on which rests the direction of her course towards the port of destination.
ARITHMETIC OF NAVIGATION.
THE first thing to be considered is-Do you understand the Arithmetic of Navigation?-if you do not, it can be explained in a few pages, and these the beginner would do well to carefully read; he who is proficient in this knowledge can pass on to the next subject-" Circles and Angles."
It is of course taken for granted that you are well up in the four rules of simple arithmetic-addition, subtraction, multiplication, and division-which are as constantly required in Navigation as in daily business transactions.
Let us begin with the arithmetic of the Circle and of Time, the parts of which in both are divided sexagesimally, or, in other words, sixty of a less denomination make one of a greater. Two short TABLES furnish us with the basis of computation.
(A) DIVISIONS OF THE CIRCLE, OR ANGULAR MEASURE.
and these terms are respectively marked °'", so that 5° 51' 28" is to be read 5 degrees, 51 minutes, 28 seconds.
but in this instance the terms are respectively marked h. m. s., 6h. 31m. 24s. is to be read 6 hours, 31 minutes, 24 seconds.