When the half of the 14-lb. stone was legally called a nail, how was this term to be rendered into law-Latin or statute French by the scribes of Plantagenet times ignorant of the origin of the term? Naturally they blundered; they got hold of the wrong nail, rendering it by L. _clavus_ instead of by _unguis_, and by Fr. _clou_, _cloue_, or in the script of the time _clove_ instead of by _ongle_. This misnomer took; and a statute of 1430 states that a Wey of cheese may contain 32 cloves, every clove 7 lb., making the wey = 224 lb., 2 Cwt. But despite statutes the cheese-trade went on with its 8-lb. clove, of which 32 make 256 lb., the true wey. It was the same with the wool-trade, controlled by the State for revenue purposes. The half-stone of wool became a nail. In 1342 we find _quatuor clavos lanæ_, 4 nails of wool. But _clavus_, a nail, became confounded with _clavis_, a key, and so in Southern France the nail-weight, introduced from England, became _clau_, a key, instead of _clavèu_, a nail. Thus the nail, Fr. _once_, _ongle_, became clove, Fr. _clou_, L. _clavis_, an iron nail; then in Prov. and Fr. _clau_, L. _clavus_, a key. 3. THE CARAT AND THE GRAIN (A) _The Carat_ One would hardly recognise the golden Solidus of Rome in the French Sol, the brass halfpenny with the effigy of Louis XVI, current within my memory, or in the bronze Sou by which sums under three francs are still reckoned in France. The Solidus, Aureus, or Exagium solidi, was so called because, representing the As, or unit of money, it was the gold-unit of which the semissis was the half and the tremissis the third. Weighing 70·1 grains (under Constantine) it was 1/6 of the Roman mint-ounce = 420-2/3 grains, or 1/72 of the As libralis. Its weight was equal to 24 siliquæ, afterwards called Carats = 2·921 grains, and its third, the tremissis, weighed nearly 24 grains, the troy pennyweight. Hence pure gold was considered as solidus or ‘entire’ of 24 carats, and the quality or ‘touch’ of gold would be denoted by the number of carats of pure gold it contained out of 24. The carat of fineness was divided into 4 assay-grains, and these again into fourths. English gold coins are 22 carats fine since the time of Henry VIII, but the Plantagenet gold coins were usually 23 carats 3-1/2 grains fine, that is 191/192 = nearly 995 in 1000. Thus the carat was 1/24 Solidus or 1/144 ounce. When the Arab caliphs had conquered Egypt and the greater part of the Mediterranean countries, they followed Roman imperial customs and replaced the gold Exagium solidi, 1/72 of the As, by the gold mithkal, 1/72 of the Libra or Egypto-Roman pound. The Mithkal was then 1/6 of the Egypto-Roman ounce = 437 grains, so that it weighed 72·7 grains. It was divided like the Roman coin into 24 qirát, each = 3·035 grains and divided into 4 hubba or light grains, meaning corn-grains.