(Con’t)
…point of starting. Similarity, if he walked from the equator, due N., his latitude would increase with (about) every 69 miles, 1°. The highest latitude he could reach would be 90° N. at the North Pole, because from the equator to the pole is only 1/4 of the full circle. The goal of Arctic explorers is, therefore, 90° N. latitude.
Fractions of degrees are measured in “minutes" (') and “seconds",("). Don't confuse them with the min.[utes] and sec.[onds] of time: this represents distance. A ' is 1/60th of a degree; and a “ 1/60th of a ' . A degree at the equator being about 69 land miles, * a ' would be about 1 1/7th miles, and a “ about 100 ft.
*A degree of latitude at the equator is exactly 60 nautical miles, and a ' therefore, exactly one nautical mile, commonly called a "knot."
Distances at sea are always measured in knots, or nautical miles. A knot, as stated, is near enough 1 1/7 miles to call it so for the purpose of rough and ready comparison. A torpedo boat having the speed of 35 knots an hour would, therefore, keep abreast of an express train making 40 miles an hour.
You can, therefore, see that there is no spot on the surface of the earth that cannot be located to within 100 feet, at most, by the intersection of two imaginary lines numbered in degrees, ‘ and “, from some defined starting point. We call these lines "imaginary”, and so they are, as a matter of strict truth, for the surface of the earth doesn't show them to the eyes. But they are marked on all maps and charts in the plainest way, and to the sailor's mind they are as definite and actual as any street line may be to you.