| At degrees | 1 | to | 3 | = 68·704 | statute | miles | ; 1/60 = 6046 ft. |
| „ | 88 | to | 90 | = 69·409 | „ | „ | ; 1/60 = 6108 ft. |
The mean length is at about 49° N. where the degree and mile are—
69·091 statute miles; 1/60 = 6080 feet.
The perimeter of the base of the Great Pyramid is exactly half of that length, i.e. 3040 feet.
The length of the meridian mile, 1000 Olympic fathoms = 4000 Olympic feet, was divided by the Greek geometers (and probably by the Egyptians and Chaldæans long before them) into 10 stadia, each of 100 fathoms = 600 Olympic feet = 608 feet, which is about our present cable length. And the meridian or nautical mile, used by seamen of all nations, is this same Egypto-Greek mile of 6080 feet = 2026-2/3 yards = 1013-1/3 fathoms = 1·1515 statute miles. It is sometimes put at 6082-2/3 feet. French geometers estimate it at 1852·227 metres = 6076-3/4 feet, one ten-millionth of the quarter-meridian being = 1·0002 metre. The nautical mile is sometimes called a knot, in the sense of a ship going so many nautical miles in an hour, as ascertained by the number of knots of the log-line, each 1/120 of a nautical mile or 50-2/3 feet, run out in half a minute, 1/120 of an hour.
The meridian mile must not be confounded with the geographical or equatorial mile, 1/60 degree along the equatorial circumference = 6087-1/3 feet.
Greek Itinerary Measures
Though a length of 10 stadia is a meridian mile, neither the Egyptians nor the Greeks appear to have used this mile as an itinerary measure. Herodotus says:
All men who are short of land measure it by Fathoms; but those who are less short of it, by Stadia; and those who have much, by Parasangs; and such as have a very great extent, by Schoinoi. Now a Parasang is equal to 30 stadia, and each Schoinos, which is an Egyptian measure, is equal to 60 stadia.
The Parasang of 30 stadia was then 3 meridian miles, the modern marine league, 1/20 of a degree.