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. parisons are made, &c., including also a computation of 
ON THE SCIENCE OF WEIGHING AND | the probable errors of the final results, 
MEASURING, AND THE STANDARDS OF The whole subject will therefore be treated under the 
AN. following general heads :— 
MAIGHT AND AOA I. Definitions of weight and measure. 
Ji II. Standards of imperial weight and measure. 
1D geeks the last few years public attention has been | _IIJ. Scale of multiples and parts of imperial standard 
frequently drawn to the subject of our national pats 7 
IV. The metric system. 
V. Weighing and measuring instruments and their 
use. 
weights and measures. The administrative and social | 
questions of oe nopervement of ous existing es: and 
of the proposed introduction into this country of the deci- eal 3 
mal ee system—first established in mone and now I. Definitions of Weight and Measure. ; 
being generally adopted on the Continent of Europe, and Weight or gravity has been defined as the quality in 
indeed extending to the other quarters of the world—have | physical bodies by which they tend towards the centre of 
formed the subjects of debate in every Session of Parlia- | the earth, in a line perpendicular to its surface ; or it may 
ment, and are still awaiting solution. The scientific ques- | be defined more generally as a property inherent in all 
tions involved in the use of weights and measures have | bodies, by which they are drawn to some common point, 
for a much longer period engaged the attention of many | called the centre of gravity, and with a velocity in propor- 
of our most eminent men of Science, several of whom | tion as they are more or less dense, and as the medium 
have been members of the various Standards Commissions | through which they pass is more or less rare. 
from time to time appointed by the British Government. In following out his discovery of the theory of universal 
These questions are also at the present time the objects | attraction and gravitation, Sir Isaac Newton demon- 
of investigation and deliberation by the large body of | strated, first, that the weights of all bodies at equal dis- 
scientific men from all civilised countries, who compose | tances from the centre of the earth are directly propor- 
the International Metric Commission at Paris. It may, | tional to the quantity of matter that each body contains ; 
therefore, be useful to bring together and place before the | whence it follows that the weights of bodies have no de- 
public the several points involved in the science of weigh- | pendence on their shapes or textures, and that all spaces 
ing and measuring, and to give some account of our stan- | are not equally full of matter. Up to the time of Newton 
dards of weight and measure, as well as to describe in | the earth was considered to be spherical, but it was de- 
some detail the scientific construction of our existing im- | monstrated theoretically by Newton, as well as by 
perial standard yard, and pound. No sufficient means have | Huygens, that the earth must be flattened at the poles. 
hitherto been adopted for making the general public ac- | Whence it was shown by Newton, secondly, that on diffe- 
quainted with this part of the subject, although they are di- | rent parts of the earth-surface, the weight of the same 
rectly interested in it, the information hitherto published | body is different, owing to the spheroidal figure of the 
respecting it having been confined to afew papers in the | earth, which causes the body on the surface to be nearer 
“ Philosophical Transactions,” and to reports of the | to the centre in going from the Equator towards the 
several Standards Commissions, and other Parliamentary | Poles; and that the increase of the weight is nearly in 
Returns. Of these papers the most important are those | proportion to the versed sine of double the latitude, or, 
on the construction of the imperial standard pound, by | which is the same thing, to the square of the sine of the 
Prof. W. H. Miller, in ‘ Phil. Trans.,” 1856, and on the | latitude. He assumed the weight at the Equator to that 
construction of the new imperial standard of length, by | at the Pole to be in the proportion of 229 to 230, and con- 
the Astronomer Royal, now Sir G. B. Airy, K.C.B., in | sequently the whole increase of weight from the Equator 
1857. In the following treatment of the subject use will | to the Pole to be the 229th part of the weight at the 
be made of these papers, as well as of other authoritative | Equator. 
works relating to weights and measures. In accordance with the principle the discovery of 
The science of weighing and measuring comprehends | which is ascribed to Archimedes, that all bodies im- 
the following points :— mersed in a liquid suffer a loss of weight precisely equal 
The scientific definition of weight and measure. to the weight of the liquid displaced, it was also demon- 
The authoritative establishment of fundamental units | strated that a body immersed in any fluid specifically 
of weight and measure of length and the construction of | lighter than itself loses so much of its weight as is equal 
their material representatives as primary standards, in | to the weight of a quantity of the fluid of the same bulk 
relation to which all numerical amounts of weight and | with itself. Hence a body loses more of its weight in a 
measure are to be expressed. heavier fluid than in a lighter one, and therefore it weighs 
The establishment of determinate aliquot parts and | more in a lighter fluid than in a heavier one, for instance, 
multiples of the primary units of weight and measure, | more in air than in water. ' 
and of other units derived from them, such as the unit of The foregoing principles laid down by Newton are — 
measure of capacity, &c.; and the construction and veri- | universally admitted as correct, with the exception of the 
fication of their material representatives, as secondary | numerical proportions of the weight of bodies at different 
standards, by comparison with which the accuracy of all | parts of the earth’s surface ; for it is important to observe 
weights and measures in ordinary use is to be ceter- | that Newton founded his calculation of the earth’s ellip- 
mined. ticity on the hypothesis of its being homogeneous, which 
The scientific methods of using standard and other | is not the case ; and hence he makes the equatorial dia- 
weights and measures in which special accuracy is re- | meter greater than the polar axis, as 230 is to 229. But 
quired, as well as auxiliary scientific instruments, such as | from the numerous experiments since made with the 
balances, thermometers, barometers, micrometers, and | pendulum at different parts of the earth, it has been found 
other comparing apparatus. that the earth is not homogeneous, or composed of con- 
The determination of the just results of weighing and | centric strata of equal density, and that the ellipticity is 
measuring with these scientific mstruments, after allowing | not so great as Newton supposed. 
for all indirect influences affecting the accuracy of the The method of measuring the intensity of gravity on 
direct results of weighing and measuring ; for instance, | different parts of the terrestrial spheroid, by means of the 
differences arising from the physical composition of | seconds pendulum, is said to be due to Borda, as origin- 
bodies, variations of temperature and consequently of the | ally described in a Memoir inserted in vol. iii. of the 
expansion or contraction of the several substances, | Base du Systeme Métrigue. From the results of Borda’s 
changes of condition in the medium in which the com- | experiments, made towards the close of the last century, 
