WEIGHTS AND MEASURES.

New Zealand Journal of Agriculture, Volume XVIII, Issue 4, 21 April 1919, Page 208

WEIGHTS AND MEASURES.

RELATION TO AGRICULTURAL PRODUCTS.

By

R. WATERS,

Biological Laboratory.

The following notes were written to meet some of the difficulties encountered by students and by. both small and large buyers and sellers of agricultural products. The difficulties arise as much from, the inconstancy of the intrepretations of terms as from the variability in the systems and usages of races and of localities.

CONSTANT, VARIABLE, AND EQUIVALENT MEASURES.

Constant measures are those of weight, volume, or extent, each, expressed by the same term, and meaning the same wherever that term is employed. v ' • Variable measures of weight, volume, or extent are such as are grouped under a single term, the meaning of which consequently differs in different connections, or in the individual conceptions of' different localities or even of the same locality. Equivalent measures are sets of constants or variables, the terms of which are synonymous and the values of which are equal.

Constant Measures

Pound Avoirdupois. —Among the English-speaking peoples of theworld the pound avoirdupois is the standard of weight for most purposes ; it goes by the same name and expresses the same weight.. This standard evolved in the following manner : In 1758 the English standard of a pound -troy was definitely laid down. This is the foundation of all legal weights. One-twelfth of this weight is a troy ounce, one-twentieth of a troy ounce is a pennyweight, and one-twenty-fourth of a pennyweight is a grain, so that 5,760 grains is a. pound troy. Later it was determined that 7,000 grains troy should constitute one pound avoirdupois. These two standards were subsequently confirmed by Acts of the English Parliament that still remain law. Moreover, this conception of a pound avoirdupois has not been corrupted by trade customs to any appreciable extent.

Gramme. -Among the majority of the civilized nations of the world, the metric. system is required by law. In Britain and the United States of America its use is permitted, and it is there c mon y employed in scientific practice. The system is largely employed in dairy chemistry, seed-analysis, &c. The gramme is the unit of weight under the metric system. 453-59 . grammes equal 1 lb. avoirdupois = 7,000grains. These equivalent weights link up the gramme with the British.

avoirdupois, and troy systems. The rough equivalent “ 454 grammes equals 1 lb. avoirdupois ” is constantly used in seed-analysis. It may be recalled that the gramme standard of . weight originated in the following way : A metre, the metric unit of length, is presumed to be the ten-millionth part of a meridian line drawn from the Pole to the Equator. The one-hundredth part of a metre is a centimetre. A cubic centimetre (1 c.c.) of distilled water is the weight of 1 gramme.

Cubic Centimetre (c.c.). — The cubic centimetre is a measure of capacity under the metric system. 1,000 c.c. equals 1 litre, the unit of capacity ; 1 litre equals 1-76 pints ; 8 pints equals 1 imperial gallon. These equivalents link up the metric with the British measures of capacity.

Variable Measures.

Ton. — The term “ ton ” is applied to a variety of both weight and capacity measurements. As a measure of weight its chief use in the British Empire is to express the weight of 2,240 lb. avoirdupois. In this connection it is sometimes alluded to as the “ long ton ” or “ gross ton.” The “ short ton,” consisting of 2,000 lb., is the.ordinary meaning of the word ton in respect to weight in the United States of America, and is thus commonly used also in Canada, South Africa, and in certain other parts of the British Empire. The metric ton consists of 2,204’6 lb. As a measure of capacity-a “ register ” ton is a unit of the internal capacity of ships ; it consists of 100 cubic feet. The “ ton ” is also the unit approximately equal to the volume of a long-ton weight of sea-water, used in reckoning the displacement .of vessels cubic feet —called specifically a “ displacement ” ton. • Again, the “ ton ” is the unit of volume for freightapproximately the volume of a ton weight of the particular - commodity. • In this case it is called a “ shipping ” ton. A ton of merchandise is often reckoned as 40 cubic feet, and a ton of timber at 42 cubic feet. The shipping ton of 40 ft. is used in New. Zealand, with fractions expressed in cubic feet.

Hundredweight. — This term is applied to various measures of weight. In the British Empire it is most commonly 112 lb. avoirdupois. In the United States and various other parts, however, it - is 100 lb. avoirdupois. The metric hundredweight contains 110-23 lb. avoirdupois. In each case the hundredweight represents one-twentieth of its particular kind of ton. - ■

Quarter. — This is a term for various measures of weight and capacity, of which more strictly it always represents one-fourth. For instance, as a quarter of a hundredweight it represents in Britain 28 lb. avoirdupois, and in the United States 25 lb. avoirdupois. As a measure of capacity the quarter represents 8 bushels. Now, 1 bushel consists of 8 gallons, and 1 gallon, the standard British imperial measure, is the capacity of exactly 10 lb. avoirdupois weight of distilled water, which occupies 277,274 cubic inches of space. Thus —1 . gallon = 277-274 cub. in. ; ( X 8) 1 bushel = 1-28 cub. ft. ; ( X 8) 1 quarter = 10-24 cub. ft. The quarter will also be seen to be approximately one-fourth of a ton as used in —namely, 10-24 cu ft. X 4 = 40-96 : hence its name. - . .

Bushel. —-This is a term for various measures of capacity and weight. Like the quarter of capacity, it is a multiple of the British imperial

standard gallon —8 gallons constituting i bushel. A bushel, therefore, is the space occupied by io lb. X 8 = 80 lb. of distilled water, and has a cubic measurement .of 277-274 cub. in. x 8 — 2,218-192 cub. in. = 1-28 cub. ft. This is called the “imperial bushel,” and applies in the British Empire.- In the United States at present, however, the term “ bushel ” is recognized as the’ space occupied by Only 77-63 lb. of distilled water, the measurement of which is 2,150-42 cub. in. This is known as the “ Winchester bushel*,” and was in early times the recognized bushel of England, being later abandoned. In various places throughout the world a bushel is actually a certain weight of a certain commodity. That weight may be a standard weight understood or enforced by law for each commodity within a certain district, country, or kingdom. Such standards, however, vary considerably in different localities. The bushel may also be a weight. assigned to each line of certain commodities according to the actual weight of a bushel of capacity. ’ •

Summary.

1 The. points of most practical value in the foregoing remarks may be briefly summarized as follows : — .. . 1. The variable measures of weight and of volume arrange themselves round and depend ’ very largely upon the ancient and constant British pound avoirdupois. Thus the ton, hundredweight, quarter, and bushel are in many of their meanings merely multiples of the. pound avoirdupois. . ’ /

2. One of the most useful equivalents in seed-analysis, and one that links up the British avoirdupois with the widely metric system of weights, is the formula—1 lb. avoirdupois equals 453-59 grammes, or, roughly, 454 grammes.

3. Another most important equivalent linking the British avoirdupois with the British standard measure of capacity is that 10 lb. of distilled water equals 1 gallon. The formulas 1,000 c.c. equals 1 litre and . 1 litre equals 1-76 pints are equivalents in constant use and connect the metric with the British imperial systems. 4. Great discretion must be exercised in commerce in the use of the terms “ ton,” - “ hundredweight,” “ quarter,” and “ bushel.” 5. It is most important to remember that 1 c.c. of distilled water weighs 1 gramme —this not only because it connects up the capacity and weight measures under the metric system, but also because this fact underlies the standard by means of which' the specific gravities of liquids and solids are compared and expressed. Specific-gravity estimations enter largely into scientific agricultural laboratory work. This cubic centimetre equivalent, together with “ 10 lb. water = 1 gallon,” is used considerably in agricultural chemistry, notably in the preparation of solutions of a definite strength per cent. Thus 100 c.c. of water plus 1 gramme of a soluble solid is a i-per-cent. solution of that solid, but 99 c.c. of water plus 1 c.c. of another liquid is a i-per-cent. solution of that liquid. ' j

LOCAL USAGE OF WEIGHTS AND MEASURES.

The more local usages of weights and measures introduce a still further set of meanings for certain of the terms just reviewed meanings which are a very fruitful source of ; misunderstanding and even of extensive deception in transactions between buyers and sellers.

The Bushel. — In New Zealand certain agricultural seeds are in general sold neither by bushel capacity nor by the pound weight. They are sold upon an entirely arbitrary weight which is called a “ standard bushel.” The bushel standards are practically universally acknowledged throughout the trade in New Zealand. They are as follows : Oats, 40 lb. ; wheat, 60 lb. ; rye-grass, 20 lb. The number of bushels in a sack or in a line of many sacks is estimated on the number of pounds avoirdupois. Thus a sack containing 1401b. of rye-grass contains 140 4- 20 = 7 bushels, and is 1 bought, quoted, and sold as 7 bushels. Again, a 48 m. sack may contain 160 lb. of rye-grass,' in which case it is reckoned as containing 160 4- 20 = 8 bushels. This kind of bushel has no connection with the bushel of capacity, which equals 1-28 cub. ft-., nor has it much real connection with the term “ bushel weight,” which is the actual weight of a definite capacity of 1 bushel = 1-28 cub. ft., as discussed later. The most that can be said of it is that it has to do with the bushel weight- inasmuch as it is the accepted bushel weight for oats, wheat, and rye-grass. The most accurate conception of the basis on which rye-grass is bought and sold in New Zealand is that the transactions are made at a price per 20lb. lot; similarly, with'wheat, at a price per 60 lb. lot; and oats, at a . price per 40 lb. lot. The standard of 40 lb. per bushel for oats, while constant in the New Zealand trade, may or may not agree with the standard of other places. For instance, the legal standard bushel in the United States for oats is 32 lb., .while in Great Britain it is 40lb. and 421b. for local, and 38 lb. and 40 lb. for foreign oats. Our standard of 60 lb. for wheat agrees exactly with that of the United States, but differs from the British, which is 631b. for local and 62 1b. for foreign wheat.

Bushel Weight. — The discussion of the term “ bushel ” naturally leads into a consideration of the term “ bushel weight,” which expresses the approximate (usually correct to the nearest pound avoirdupois) weight of a volume of seed measuring 1 bushel or 1-28 cub. ft. The intrinsic value of the amount covered by the expression “ bushel weight ” depends upon two factors—namely, the true density and the apparent density of the seeds. True density : In physics this is the ratio of' mass' to bulk (or volume) of matter. In seed work the bushel weight is raised or lowered according to the. density of the various parts of each seed. The density of the compact moist mass of starch, &c., constituting the kernel of ryegrass, for instance, is greater than that of the dry aggregation of empty cells constituting the chaff. If, then, the individual seeds of a line have very large kernels, as in certain Canterbury ryegrasses, or large kernels as compared with the weight of the chaff after dressing, as is strikingly exhibited in certain Hawke’s Bay lines, then the total density of each seed is very great, and the weight of a bushel is —perhaps 35 lb. If, on the other hand, another line, possibly through an unfavourable season, immaturity at harvest-time, or bad or long storage, consists of kernels that are shrivelled or small in relation to their chaff (or glumes), then a greater proportion of the seed consists of chaff than in the first instance, and the total density of each seed is less and the bushel weight lowperhaps as low as 25 lb. per bushel. From this it will be seen that the variation in bushel weight arising from true density in a seed like rye-grass that has such a large chaffy covering must be much greater than the variation . from the same cause in the bushel weight of wheat, which is practically all kernel. ,

Apparent density : This refers to the density not of the. individual seeds, but of the seeds together with the air-spaces about them just ■ as they naturally lie in bulk. The principle involved can well be represented by a box of small shot and a box of larger shot made of the same material. Placed on the scales it .will be seen that the small shot weighs heavier than the larger size. The reason for this is that in the case of the small shot the sum'total of the air-spaces is less than in the case of the larger shot. This fact can be easily proved by filling the air-spaces in each case with water and pouring it off into a measure. It will therefore be seen that small seeds show a greater apparent density, and consequently a greater bushel weight than large seeds. Thus certain . Hawke’s Bay ryes show bushel weights greatly increased merely on account of the small size of their members, while certain Canterbury ryes are lowered in bushel weight largely on ' account of the greater size of their members. When, as in the case of some Hawke’s Bay and other lines, the true -density of each seed has been increased by the removal in the dressing of as much of the chaff as possible, and the apparent density is also high by reason of the small size of seed, very high bushel weights are sometimes obtainedas much as 40 lb. per bushel. - . . ’. ■ The influence of the apparent density upon the bushel weight of seeds is very frequently quite overlooked. To a large extent the popular view is that seeds of a heavier bushel weight are relatively better than those of a lighter bushel weight because the former indicates that the kernels of the seeds are well developed, and as it is the kernel that has to grow there is some assurance that seeds of a high bushel weight will be of good germination capacity. Moreover, large seeds are perhaps rightly believed to produce large and vigorous plants. Such a conclusion is often formed entirely with the idea that bushel weight is purely an indicator of true density ; it pays no regard to apparent density, which may greatly negative the high results arising from true density. A conclusion of this kind is in some cases accidentally true, but in others quite erroneous. Were it not that we have many seed-sellers of undoubted repute the bushel weight of seeds in quotations would generally be of doubtful value. When the germination capacity is not quoted it therefore behoves every buyer, where possible, to inspect or have inspected a sample of the seed offered, if for no other reason than to ascertain that the bushel weight quoted is not in reality obscuring undesirable qualities, such as small immature seeds, heavily dressed. If, however, the seeds are somewhat small but plump, as in the case of most Hawke’s 'Bay rye-grasses, then despite heavy dressing they are probably excellent seeds.

Concrete for Small Sheep-dipping Plant. — On page 9 of the Journal for January last were given the quantities of concrete required for the dip and draining-floor of the one-man sheep-handling plant recommended by the Department. A correspondent writes pointing out that the information would be more useful to the average farmer stated in terms of the quantities of the different materials required for the job. These are approximately, as follows for a 1-2-6 mixture : . Cement, 5| barrels of 3761b., or 17 bags- of 1241b.; sand, i| cubic yards; gravel, 4| cubic yards.