This new measure is the cubit of Ezekiel, the ‘great cubit,’ the ‘cubit and a handbreadth,’ = 25·26 inches.
The same question as that presented by the increased cubit of Egypt arises in the case of the Assyrian cubit. What reason can be suggested for an increase such as to again disturb the palm and the digit? The advantage of having a standard of 8 palms divisible into 2 feet of 4 palms, could have been obtained far more simply and conveniently by adding an eighth palm equal to the others, making it 23·6 inches, with a half giving a foot = 11·8 inches. Or two palms might have been added to the common cubit, making a new cubit = 24·32 inches, with the Olympic foot as its half.
I again venture a similar explanation. The increase from the length of the Egyptian royal cubit corresponds to the ratio of the degree of longitude to the degree of latitude in 35·5° N., i.e. 1 : 1·224—
This position was only 30 meridian miles from the parallel of 36° N., a line which, passing through Rhodes and Malta to the Straits of Gibraltar, was considered by the ancient geographers as the first parallel and was the base-line of their maps. It was called by the Greek geographers the ‘diaphragm of the world.’[4]
Διάφραγμα τῆς ὀικουμένης. Instituted by Dicæarchus 310 B.C., corrected by Eratosthenes 276-196.
This line passing also a few miles south of Nineveh, it is possible that some observatory near that capital city, a few miles south of 36°, may have been the point at which the difference in the lengths of the degrees of longitude and of latitude was determined for the standard length of the new cubit.
There is an alternate hypothesis. The Egyptian royal cubit was increased by 1·224 to make the Great Assyrian cubit. Now this is about the proportion in which a measure containing a certain weight of water must be increased in height to contain the same weight of wheat. This proportion, the water-wheat ratio, is something between 1·22 and 1·25, the former being the usual ratio with the heavier wheat of Southern countries. Supposing a cubical vessel measuring a royal cubit of 20·64 inches in each side, therefore containing 8792 cubic inches = 317 lb. of water (which was the Great Artaba) to be increased in height so as to hold the same weight of wheat, its height would now be 1·224 × 20·64 = 25·26 inches. This might have been taken for a new cubit.