2. The Imperial Pound
It is the weight in vacuo of a certain piece of platinum kept in London. It is divided into 16 ounces, approximately Roman ounces. The ounce may be divided into 16 drams.
The pound is also divided into 7000 grains, the ounce being 437-1/2 grains.
It may be well to anticipate or remove any uncertainty about the grain. The averdepois pound was only divided into ounces and drams (just as the yard is only divided, as a yard, into quarters and nails), but on its adjustment with the troy pound as = 7000 grains of which the latter = 5760, it became divisible into grains. These were long called Troy grains, in consequence of the superstition about the noble Troy weight. This word seems to have paralysed the intelligence of many persons doubtless sensible enough in other matters; thus Rees’ ‘Cyclopædia’ (1819) informed its readers that ‘the pound or 7680 grains avoirdupois equals 7000 grains troy, and hence 1 grain troy equals 1·097 avoirdupois.’
The weight of the standard pound in a vacuum (that is, its weight not diminished by the buoyancy of the air) being 7000 grains, a commercial brass pound exactly equal to the platinum standard when weighed against it in air at 62°, would weigh 7000·6 grains in a vacuum.
The Dram
This, 1/16 of an ounce = 27-1/3 grains, is principally used as a unit for powder in the cartridges of sporting guns. In Scotland it was called a ‘drop.’
1673. A quech weighing 18 unce and 10 drop.
1805. An arrow of from 20 to 24 drop weight (‘N.E.D.’).
The dram was possibly so called from its corresponding to the quentchen, 1/8 of the German Loth or half-ounce (1/16 of a marc) as the drachm was 1/8 of a medicinal ounce.[[24]] Or it may merely have been called a dram as being the part of the ounce, in the same way that the drachm was the next lower part of the apothecaries’ ounce.