3. The Pride and Fall of Troy
The myth of the 32 wheat-corns which formed the basis of the Tower pound = 5400 grains, passed to the Troy pound = 5760 grains, and this deliberate fiction lasted till the time of Elizabeth and perhaps later. It did little harm as regards these mint-pounds, but its application to the Averdepois pound, alleged to be an offshoot of the royal pound, either as 25 shillings, that is 300 pennyweights of 32 wheat-corns, or as 15 ounces Troy, or at a later period as 16 ounces Troy, produced a mental obliquity which is most lamentable.
The jury of merchants and goldsmiths appointed in 1574 to examine the ancient standards, and construct a new set, declared that ‘the one sorte of weight nowe in use is commonlie called the troie weight and that other sorte thereof is also commonlie called the avoir de poiz weight, and further they say that both the saide consiste compounded frome thauncient Englishe penye named a sterling rounde and unclipped which penny is limeted to waie twoo and thirtie grains of wheate in the midest of the eare and twentie of those pence make an oz. and twelf of those ounc make one pound troie.’ They go on to ‘saie that the said twoo sortes of weights doe differ in weight the one from the other three ounces troie at the pounde weight, for the pounde weight troie doth consiste onlie of xii oz. troie and the lb. weight of avoir de poiz weight dothe consiste of fiftene ounc troie.’
Thomas Hylles, in his ‘Arte of Vulgar Arithmeticke’ (1600), showed himself emancipated from the superstition of troy weight so far as to say:
‘15 ounces of Troy weight should by the statute make 1 pound of haverdepoise, but the same pound weyeth commonly but 14 ounces 1/2 Troy, 14 ounces 3/5 at the uttermost.’
(14-1/2 oz. troy = 6960 grs.; 14-3/5 oz. = 7008 grs.)
But he unfortunately went on to say that ‘of things liquid and dry 1 pound of Troy weight maketh a pinte in measure,’ not seeing that 12 oz. troy = only 13·16 oz. averdepois, while a wine-pint contained 16-2/3 ounces of water, and a corn-pint close on 16 ounces of wheat or 20 of water.
But the ignorance and superstition engendered by troy weight was just as bad in 1702 as in 1600 or even in 1500, as shown by the following utterance of an eighteenth-century scientist:
Troy weight, whereby bread, gold, silver, apothecaries’ wares etc. are weighed containing only 12 ounces in the pound, each ounce 20 pennyweight each pennyweight 24 grams. This seems to have been the most ancient weight by its name, as derived from the famous city of Troy, from whence Brutus and his people are said to have descended and to have called London Troy-Novant or New Troy.
So said J. Ralphson, F.R.S., in his ‘Mathematical Dictionary’ (London, 1702). And then he continued:
The second and more common weight is called Avoirdupois, being fuller and larger weight than the other, for it contains 16 ounces or 128 drams, viz. 384 scruples, viz. 7680 grains, by this are weighed all kinds of grocery ware and base metals, as iron, copper and brass, as also hemp, flax, rosin, pitch, tar &c.
A century later we find not much improvement in the idea of the pounds Troy and Averdepois.
‘The pound or 7680 grains avoirdupois equals 7000 grains troy and hence 1 grain troy equals 1·097 avoirdupois’ (Rees’ ‘Encyclopædia,’ 1819). This is an example of the utter muddle the Troy pound had made in the minds of otherwise intelligent people.
Similar pedantic efforts were continued, well into the nineteenth century, to represent the Troy pound as the sole standard of England and the averdepois pound only respectable as an offshoot of the royal pound used for vulgar purposes.
The Assize of Bread
Such fictions were helped by the old statutes which compelled the sale, first by Tower and then by Troy weight, of bread as well as of gold, silver, and medicines. And confusion was made worse by the use for a long period of a third weight for bread, the Amsterdam or Scotch troy pound.
The peck loaf, supposed to be that produced from a peck of flour (16 pints), was to weigh 16 of these pounds = 17 lbs. 6 oz. averdepois, the quartern loaf 4 = 4 lb. 5 oz., and the pint loaf (to be sold at a penny when wheat was 4s. a bushel or 32s. a quarter) was to weigh one pound = 17 oz. 6 drams averdepois. The periodical Assize of Bread fixed the price of the peck loaf.
It appears then that the pound of bread was = 7600 grains, its ounce = 475 grains, which was about the Scottish (and Dutch) troy standard. It was probably adopted as coinciding with the weight of bread supposed to be produced from a pint of flour and as keeping up the old superstition that bread must be sold by troy weight. As some persons in authority did not share the stupidity of those who considered the averdepois pound to be 16 troy ounces, the Scottish 16-ounce pound of troy standard was imported for the purpose.
This weight was abolished by 8 Anne (1710) and the sliding scale was put in the averdepois equivalent.
The Assize of Bread was abolished in 1815, but traces of it remain in the name ‘quartern loaf,’ although this now means a loaf of 4 imperial pounds. It may also mean a loaf weighing the quarter of a 16-lb. stone.
The Disappearance of the Troy Pound
In 1841 a Royal Commission on Weights and Measures recommended the abolition of the Troy pound as ‘wholly useless,’ retaining its ounce provisionally for the use of bullion merchants, pending ‘the removal of the troy scale.’ This recommendation was not carried out until 1878, when the Troy pound disappeared, except of course in almanacks and books for the instruction of youth—but the Troy ounce still survives at the mint, and consequently in the bullion market; and it is virtually forced on druggists in spite of the Medical Council. Troy weight was abolished by the Pharmacopœia Committee in 1864, Imperial weight being alone recognised; yet the Board of Trade keeps up the Apothecaries’ ounce of 480 grains. Troy weight has fallen; but, like many other superstitions, it dies hard.
CHAPTER X
THE CUBIC FOOT AND THE TON REGISTER
The cubic foot and the cubic inch are the usual measures of solidity. The cubic yard is used as a measure of masonry, earthwork, or reservoirs of water.
The cubic foot has many points of concordance with weights and with measures of capacity, and is the basis of ship and cargo measurement.
The definition of the Imperial gallon as 277·274 cubic inches, the volume of 10 lb. of water at 62°, a pound of water measuring 27·7274 cubic inches, led to attempts to determine accurately the weight of a cubic inch and of a cubic foot of water. These experiments are interesting in consequence of the recognition, in 1685,[[29]] that the cubic foot of water weighed approximately 1000 ounces, and of the probability that this weight of water in Roman ounces, = 437 grains, was the source of our Imperial system. It has already been shown how difficult it is either to construct accurately a measure containing a certain weight of water or conversely to determine the weight of water in a standard measure.[[30]]
The statute definition of the cubic inch of water as = 252·458 grains at 62° corresponds to 62·326 lb., or 997·21 ounces, for the cubic foot. Reduction of these weights to the standard of maximum density of water at 39·2° increases the weight of the cubic inch by 0·29 grain, and of the cubic foot by 1·1 ounce, making it = 62·4 lb. or 998·3 ounces. An Order in Council of 1889 gives 252·286 grains as the weight of the cubic inch of water. But the exact weight is uncertain, and the 1824 statute definition seems to be as accurate as the more recent determinations, all different.
It may be taken that the cubic foot of water weighs very approximately—
| at 62° | in air | 997·2 | ounces | |||
| at 39·2° | in air | 998·3 | „ | (+ 0·9 | ounce | ) |
| at 39·2° | in vacuo | 999·6 | „ | (+ 2·4 | „ | ) |
And 1000 ounces of water at the original weight of the averdepois ounce, of Roman standard = 437 grains, would weigh 999·5 of such ounces, at 62° in air.
Practically measures of capacity need only approximate coincidence with standards; they are used for convenience in order to avoid weighing, especially in retail trade. Corn and many other kinds of produce are more conveniently measured than weighed, the average weight being ascertained, if desired, by a sample bushel.
Fluids may also require corrections for temperature when bought or sold by measure. Water increases in volume 1 per 1000 between 39° and 61°; and another 1 per 1000 between 61° and 70°; other fluids have their peculiar coefficients of expansion.
Allowing then for small temperature-corrections, the cubic foot may be taken as equal to 62-1/2 lb. or 1000 ounces of water, and at this sufficiently approximate standard it becomes the basis of a series of measures for ship and other purposes.
The Ton Register
The capacity of ships has for centuries been reckoned in tons. The term arose from the custom, in French and other wine ports, to take as the unit of cargo-bulk the tun of wine usually contained in four hogsheads, each of 63 wine-gallons. The number of hogsheads divided by 4 gave the tonnage to be charged.
This cargo-ton, the tonneau d’encombrement, was equal to 42 French cubic feet = 51 English cubic feet.
The Ton Register appears to have arisen in the ports of Northern Europe. There the unit was usually the skippund (ship-pound) of about 360 lb. for wool and light goods. But the Last was also a wide-spread, though variable, measure; in the Baltic trade it was usually reckoned at 11-1/4 quarters of wheat = 90 bushels or 5400 lb. In England it was usually 10 quarters = 80 bushels = 5000 lb. Now this bulk of wheat measures about 100 cubic feet, so 100 English cubic feet has become the unit adopted in all maritime countries, as the Ton Register. In France it is called the tonneau de jaugage and is taken as = 2·83 cubic metres.
A ship of 2000 tons register is of a capacity = 200,000 cubic feet below decks. The register tonnage is thus obtained:
Mean length × 0·94 of maximum beam × depth from upper deck to keel, the measure being taken inside, and in feet. The product is cubic feet, which divided by 100 gives register tonnage.
In France these measurements have to be made in metres; the product in cubic metres is divided by 0·38 to get tonnage.
Net tonnage, as distinguished from gross tonnage, is the latter less the space occupied by cabins below deck, by engines and bunkers, in short all that is not ‘hold.’
This deduction gives the space available for cargo, a very large proportion in a sailing-ship, a very small proportion in a steam-yacht or tug.
The Cargo Ton is usually reckoned at 40 cubic feet; the space occupied by 20 centals = 4 quarters of wheat, or 25 centals of water.
A steamship of 4500 tons register may be 3000 tons net; as each of these net tons will contain 2-1/2 tons of cargo of about the same weight as wheat, after allowing for cases, dunnage, &c., the ship may be described as carrying 7500 tons dead-weight. Of course, this would only apply to goods of medium weight; not to iron rails or to ore, which could only be taken as a limited part of the cargo, the rest of the space being either filled with light goods or remaining empty.
The ship-owner has the choice of charging freight by measurement, usually at 40 c. ft. to the ton, or by the ton weight for metal and other heavy goods.
Concordance of Capacity, Weight and Measurement
| Capacity | Weight of Water | Cubic Inches | Weight of Wheat Lb. | Cubic Feet | ||||
| Oz. | Lb. | Oz. | ||||||
| 1 | 1·73 | 1/1000 | ||||||
| (1/2 Quartern) | 2-1/2 | |||||||
| 10 | 1/100 | |||||||
| × 8 | = Pint | 20 | = 1-1/4 | 34·6 | 1 | |||
| 100 | 5 | 1/10 | ||||||
| × 8 | = Gallon | 160 | = 10 | 277-1/4 | 8 | |||
| 62-1/2 | 1000 | 50 | 1 | |||||
| × 8 | = Bushel | 80 | 2218 | 64 | ||||
| Cental | 100 | 2 | ||||||
| × 8 | = Quarter | 500 | 10 | |||||
| × 4 | = Ton-cargo | 2000 | 40 | |||||
| = Ton-register | 10 Qrs. | 5000 | 100 | |||||
| With | the | Corn-bushel (U.S.) | = 62-1/2 | lb. | of wheat, | 1 | Quarter | = 500 lb. |
| „ | „ | Imperial bushel | = 64 | lb. | „ | 1 | „ | = 512 lb. |
Table of Volume and Weight of Water
at Different Temperatures
| Expansion | Density | Weight of | Corrections | ||||
| Temperature | —— | —— | 1 Cubic Foot. | from 1000 ozs. | |||
| Fahr.° | 1000 Units | 1000 Units | Ounces | in 1 Cubic Foot. | |||
| of Volume | of Weight | ||||||
| 32 | 1000·13 | 999·8 | 998·1 | ||||
| 39·2 | 1000 | 1000 | 998·3 | -1·7 | oz. | ||
| 45 | 1000·1 | 999·9 | 998·2 | -1·8 | „ | ||
| 50 | 1000·25 | 999·75 | 998 | -2 | „ | ||
| 55 | 1000·55 | 999·4 | 997·7 | -2·3 | „ | ||
| 60 | 1000·9 | 999·1 | 997·4 | -2·6 | „ | ||
| 62 | 1001·1 | 998·9 | 997·2 | -2·8 | „ | ||
| 65 | 1001·5 | 998·6 | 996·8 | -3·1 | „ | ||
| 70 | 1002 | 998 | 996·3 | -3·7 | „ | ||
| 75 | 1002·6 | 997·4 | 995·7 | -4·3 | „ | ||
| 80 | 1003·3 | 996·7 | 995 | -5 | „ | ||
| 85 | 1004 | 996 | 994·3 | -5·7 | „ | ||
| 90 | 1004·8 | 995·2 | 993·5 | -6·5 | „ | ||
| 95 | 1005·7 | 994·3 | 992·6 | -7·4 | „ | ||
| 100 | 1006·8 | 993·2 | 991·5 | -8·5 | „ | ||
[29]. ‘Some Gentlemen at Oxford in 1685 determined the weight of a cubic foot of spring water, or 1728 solid inches, to be 1000 ounces averdepois.’—Kelly, Metrology, 1816.
[30]. For this reason the custodians of the metric system have abandoned the cubic decimetre of water as the basis of measures either of capacity or of weight. The kilogramme is now, like our pound, a certain metal standard, and the litre is a measure containing, more or less exactly, a kilogramme of water. A perfect litre standard contains 1000 grammes of water at 39·2°; but 1·1 gramme less at 62°, 2 grammes less at 70°, and 3·3 grammes less at 80°, a very frequent summer temperature. For exact correspondence of measure with weight, corrections are always required whether on the imperial or on the metric system.