Troy grain are the same things. It thus appears that the Troy grain is nothing more than the barley-corn, which was used as the weight unit in preference to the grain of wheat in some parts of the Roman empire. Furthermore this relation between barley-corns and wheat-corns can be proved to be a fact of Nature. In September, 1887, I placed in the opposite scales of a balance 32 grains of wheat "dry and taken from the midst of the ear," and 24 grains of barley taken from ricks of corn grown in the same field at Fen Ditton, near Cambridge, and I thrice repeated the experiment; each time they balanced so evenly that a half grain weight turned the scale. The grain of Scotch wheat weighs ·047 gram, the Troy grain = ·064, ·047 × 4 = 188, ·064 × 3 = 192. Practically 4 wheat grains = 3 Troy grains.
Before passing from the Greek and Roman standards I may add that even higher denominations than the siliqua were expressed by the seeds of plants. The Romans made the lupin (lupinus) = 2 siliquae and under its Greek name of thermos ([Greek: thermos]), it was assigned a like value (Metrol. Script. I. 81). In the Carmen de Ponderibus (Metrol. Script. II. 16), 6 grains of pulse (grana lentis) are made equal to 6 siliquae, and a like number of grains of spelt are given a similar value.
We next advance towards the East and take up the Semitic systems. We have already had occasion to touch upon that of the Arabs when dealing with the modern Persians. "There can be little doubt," says Queipo (I. 360), "that the Arab system of weight was based on the grain of wheat." The habba was their smallest unit. Four habbas are equal to 1 karat, the latter of course representing the keration or siliqua, and the former the 4 sitaria or wheat-grains, which we saw were its equivalent. This is the most ordinary value given to the karat in Makrizi and the other Arabic writers on Metrology, but occasionally we find the karat made equal to only 3 grains, which of course are barley-corns. We saw above that in the Persian system the nashod was formerly divided into 4 habbi of ·048 gram (which is plainly the weight of the wheat-grain), whilst now it is divided into 3 grains each of ·063 which represents the barley-corn, or in other words the Troy grain of ·064 gram. Of course the objection might be raised that as the Arabs had borrowed their higher de-
