56 
POPULAE SCIENCE EEVIEW. 
after mature deliberation rejected tbe unit of tbe pendulum, 
and decided in favour of a standard to be deduced from the 
dimensions of tbe earth itself. An arc of the meridian, that 
comprised between Dunkirk and Barcelona, was measured in 
the most elaborate and careful manner, and by means of this 
arc, and of that previously measured in Peru, the length of 
the quarter of the meridian, or the distance from the pole to 
the equator (supposed at the level of the sea), was calculated. 
This length was sub-divided into ten million equal parts, and one 
of these parts was taken for the fundamental unit of the new 
system, and to this unit the name metre ” {iklv excellence) was 
given, from the Greek word jiirpov, which signifies measm^e. 
Objections have been urged again and again against the 
exactness of this terrestrial arc. We have even been told 
that the meter itself would have to undergo material alter- 
ation if a more accurate survey and a fresh system of 
triangulation were undertaken. Such objections, however, 
are more fanciful than real, at least as it regards the meter, 
which is really the only question we have to consider. The 
length of one minute, or sixtieth of a degree (called a nautical 
mile in French), is, according to Briot^s Arith., equal to 
1852 meters. This tallies with a geographical mile estimated 
in English yards, which is equal (in round numbers) to 2025 
yards, the meter being equal to 39|- inches nearly. Now 
if we multiply the former number by 60, and the product by 90, 
we shall have the length in meters of the quadrant of the circle : 
1852 X 60 X 90 = 10000800, which is 800 metres in 
excess of the supposed subdivision. Let us now suppose, for 
a moment, that the French savans had made an error equal to 
800 m. in their calculation : this error, although great in abso- 
lute amount, is relatively small on the meter, with which we 
are concerned ; the error (relative) would only amount to 
To 0^0 0 0 :> would be less than one twelve-thousandth (tywto)* 
We think this approximation quite sufiicient for all practical 
purposes ; and, taking all things into account, along with the 
spheroidal form of the earth, it is probable that the relative 
error is even less. Be this as it may, we need no longer con- 
cern ourselves about the original standard, whether it be exact 
or whether it be fanciful; such objections as those alluded to, 
are like dust in the balance when compared to the whole of 
this invaluable system. The standard with which we have to 
do is the model in platinum preserved in the archives at Paris, 
which can never be lost, for it exists not only in the primary 
unit, but also in those derived from it. And even were all 
the standards destroyed, if such a case were possible, they 
might again be recovered without the labour of a direct 
remeasurement of the terrestrial arc, by the known relation 
