YOUNG SEAMEN AND Y A OHTSMEN.

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 ŞEA, 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.“

60 seconds (“). ... make . . . . 1 minute (

60 minutes . . . . .

. . . . l degree o and these terms are respectively marked o!", so that 5° 51' 28" is to be read 5 degrees, 51 minutes, 28 seconds.

(B) MEASUREMENT OF TIME..

60 seconds (s.). ... make, ... 1 minute (m.)

60 minutes,... i ; , . . . . 1 hour (h.) but in this instance the terms are respectively marked h. m. 8., so that 6b. 31m. 248, is to be read 6 hours, 31 minutes, 24 seconds. ; i .