MATURE 
137 
THURSDAY, JUNE 23, 1870 
THE UNIT OF LENGTH 
HE battle of the Standards is over, and we may say 
the Metre has gained the victory. The need of a 
new system of weights and measures to amend the strange 
diversities which disfigure our practice being admitted, 
the question has once more been started—Should we 
once for all found our system ona natural basis? The 
pendulum vibrating seconds in a certain latitude, was 
long ago proposed as a universal basis of linear measure, 
and the House of Commons somewhat countenanced 
it years ago, by prescribing that the length of the yard 
shall be determined by the length of the second’s pen- 
dulum. But the action of gravitation on which the 
terms of the vibration depends, is subject to so many 
variations and disturbances, that the quantity sought 
cannot, even on the same spot, be absolutely the same 
at all times. The real length of a normal pendulum 
is almost unattainable, so limited is our knowledge of 
the force of gravity on land and at sea. A more certain 
basis for a natural unit has been found in the polar axis, 
the length of which, according to Sir John Herschel, bears 
a close relation to our imperial inch, and has the advan- 
tage of avoiding the many causes of error resulting from 
the physical peculiarities of the countries through which 
any measured arc may happen to pass. But are our 
physicists agreed as to the real length of the polar axis, 
and would it be worth while to make any alteration in our 
weights and measures for the sole purpose of attaining 
some scientific correspondence between the unit in use 
and a unit founded on nature? 
The advocates of the metre rest their arguments on a 
much broader basis. They do not assert that the metre is 
absolutely and mathematically the ten millionth part of 
the quadrant of the earth; they know that the meridians 
of places differing in longitude are not all precisely of the 
same length; and they admit that were we now to make 
a new measurement with our better instruments and 
more extended information, we might attain much greater 
accuracy than was arrived at by the French philosophers 
at the end of the eighteenth century. What commends 
the metre above any other unit, is the fact, that it is 
already a cosmopolitan unit, widely recognised, and in 
general use among many nations ; and that whilst other 
units remain as philosophical abstractions, the metre is 
the basis of a system, not only perfectly complete, homo- 
geneous, and scientific, but simple and practical in all 
its parts. Any slight error in the determination of the 
metre, is more than counterbalanced by the extreme 
simplicity, symmetry, and convenience of the metric 
system ; and not the least of its recommendations are, 
that the unit of linear measure applied to matter in its 
three forms of extension, viz., length, breadth, and thick- 
ness, is the standard of all measures of length, surface, 
and solidity; and that the cubic contents of the 
linear measure in distilled water at a temperature of 
great contraction, furnish at once the standard weight 
and measure of capacity. 
When we said that the battle of the Standards is over 
and that the Metre has gained the victory, it was meant 
that, for practical purposes, all opposition to the introduc- 
VOL, II. 
tion of the metric system has been abandoned, and that 
Parliament and the Government are now left to intro- 
duce it in such a way and at such a time as may be 
found at once practicable and satisfactory. The use of 
the metric system has been legalised for the last half- 
dozen years, but it was not till quite lately that the whole 
question was submitted to the calm deliberation of a Royal 
Commission. The Standard Commissioners, who in- 
cluded among their members the Astronomer Royal, the 
President of the Royal Society, and the late Master of 
the Mint, considered the question of the introduction of 
metric weights and measures, in any form, aé ¢zztio. And 
after careful examination they gave their verdict in its 
favour in the following terms :— 
“ Considering the information which has been laid before 
the Commission,— 
“Of the great increase during late years of internationa 
communication, especially in relation to trade and com- 
merce ; 
“Of the general adoption of the metric system of weights 
and measures in many countries, both in Europe and 
other parts of the world, and more recently in the North 
German Confederation and in the United States of 
America ; 
“Of the progress of public opinion in this country in 
favour of the metric system as a uniform international 
system of weights and measures ; 
“And of the increasing use of the metric system in 
scientific researches and in the practice of accurate 
chemistry and engineering construction ; 
“We are of opinion that the time has now arrived when 
the law should provide, and facilities be afforded by the 
Government, for the introduction and use of metric 
weights and measures in the United Kingdom.” 
The Commissioners further recommended that metric 
standards, accurately verified in relation to the primary 
metric standards at Paris, should be legalised; that veri- 
fied copies of the official metric standards should be pro- 
vided by the local authorities for inspectors of such dis- 
tricts as may require them ; and that the French nomen- 
clature, as well as the decimal scale of the metric system, 
should be introduced in this country. The Commis- 
sioners, whatever might have been their predilections, 
could not resist the fact that the civilised world pro- 
nounced itself for the metre, and they sanctioned its 
legalisation. What is to be regretted is that they stopped 
there. Since the complete substitution of the metric 
for the present practice is now practically certain, would 
it not be much better to preparé for the change and 
carry it into effect as speedily as possible? No adyan- 
tage can come froma policy of indecision, and we trust 
that the Legislature may adopt a more definite course 
than the one sketched out by the Royal Commissioners. 
Let it not be imagined that the people will give themselves 
the trouble of learning the new system, however beautiful 
and easy, so long as its use is not absolutely necessary. 
With all the desire of the teachers to introduce it in the 
schools, they find that they cannot teach the old and the 
new tables. They cannot afford the time. A compulsory 
measure is the only method of dealing with the question. 
The Warden of the Standards being now employed in 
procuring Metric Standards, it may be well to add that 
the mode of constructing them, either from the original 
Metre at the Archives, or from the copy at the Conserva- 
toire des Arts et Métiers, has been much debated. The 
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