A certain record of this cubit remains in the Great Pyramid. It is known to have measured 500 cubits along each side of the base, 2000 cubits or 500 fathoms being the perimeter of the base. The measurement made by our Ordnance Surveyors gave 760 feet for the side. The latest measurement, by Mr. Flinders Petrie, is not quite 6 inches longer. Taking the Ordnance Survey figure we have (760 × 12)/500 = 18·24 inches as the length of the common cubit, and two-thirds of this gives 12·16 inches for the common foot, or the Olympic foot as it is called from the adoption of this standard by the Greeks. This length, supported by measurements of other ancient monuments, may be regarded as certain. Four cubits or six Olympic feet were contained in the Egypto-Greek orgyia or fathom, and this measure = 72·96 inches or 6·08 feet, is exactly one-thousandth of the 6080 feet length of the Meridian or Nautical Mile. This cubit, common to the three great ancient kingdoms, Babylonia, Egypt, and afterwards Assyria, originated probably in Chaldæa, passing to Egypt with the earliest civilisation of that country, and thence to Greece. The name of Olympic thence attached to this standard must not make us forget its origin. The saying of Sir Henry Maine, ‘Except the blind forces of nature, nothing moves in the world which was not Greek in its origin,’ is not exact unless we include as Greek the great kingdoms conquered by Alexander, and which, under the Roman empire and afterwards under the Saracen caliphates, continued to have great influence over the civilisation of the West. _The Meridian Mile_ At least sixty centuries ago the Chaldæan astronomers had divided the circumference of the earth, and of circles generally, into 360 degrees (that is 6 × 60) each of 60 parts. There is good reason to believe that they, before the Egyptians, who had the same scientific ideas, had already measured the terrestrial meridian and determined the length of the mean degree and of its sixtieth part, the meridian mile. Owing to the flattening of the globe towards its poles, meridian degrees are not of equal lengths; they increase in length from the equator, so that their sixtieth parts are— 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.