How a ship finds her way to sea.
1st- How shall the position of a ship be found, and when found, how located?
2nd - What course shall be steered that will make the shortest and safest line to the destination?
The matter of the location should be explained first, because it includes the use of the words “latitude” and “longitude”, which must be repeated frequently, here after.
You see, it is necessary to get at some definite marking of a position in mid-ocean, and mid-ocean has no marks on it. Even though the navigator knew exactly how far his ship had sailed from a certain point and what direction, how could he describe the locality briefly and accurately to another? Suppose you said to a friend: "I walked up Broadway from the Battery, 3 miles, 2 rods and 1 yard, and there fell over a loose stone: be careful of that stone when you pass it” Of what real benefit would that warning be? But if you said "look out, there's a dangerous spot in the N. W. Corner of 42nd St. and Broadway” that location mean something.
By using the terms "latitude" and “longitude” a sailor fixes places as definitely as you could by using the intersection of streets, and in about the same manner. It seems worthwhile to go into this matter briefly for the sake of clearness further on.
One Hipparchus, a Greek, who thought the world was flat and that the sun revolved around it, and who lived centuries before Christ, devised this plan of marking localities. He divided up the surface of his funny, flat little world. Into small squares by drawing equidistant lines from top to bottom, and from side to side of his map. These lines being numbered, it was easy to fix any locality by mentioning the two lines that crossed each other at the spot. Twenty-one hundred years of study have developed no better method of….
(Con’t)
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