The Metrical System 427 



It was perfectly recognised by Laplace's committee that 

 for economical purposes the natural unit without an artificial 

 reproduction is useless. The suggestion of the unit is taken 

 from nature, and it is repeated as nearly as possible in 

 a mass of metal. It is the length of this mass of metal 

 at a conventional temperature which is thenceforward the 

 statutory unit. There was, therefore, no difficulty in selecting 

 a convenient length, within the above limits, for the standard 

 nautical mile. If, for instance, the minimum or equatorial 

 value for the minute of arc were chosen, and it were divided 

 into one thousand parts, to be called fathoms, each such new 

 fathom would be only three-quarters per cent., or about half 

 an inch, longer than the existing fathom ; if the maximum or 

 polar value were chosen, the new fathom would be one and 

 a quarter inches longer than the old one ; while if the length 

 of one minute of arc of the great circle of the sphere, the 

 volume of which is the same as that of the earth, were taken, 

 the difference would be one and one-third per cent, or not quite 

 one inch. Even the greatest of these rectifications is insig- 

 nificant. When applied to the yard, or half-fathom, it is 

 proportionately less noticeable, and when applied to the 

 foot it would be imperceptible without careful measurement. 

 It must be regretted by everyone that, when so simple a unit 

 was already universally adopted, and decimally subdivided, it 

 was not chosen as the fundamental unit of the system. The 

 folly of the actual selection is sufficiently shown by the fact 

 that not even in ranee has the metrical system been adopted 

 in navigation, and still less in the subdivision of the day which 

 forms an integral part of the system. Had the nautical mile 

 been selected as point of departure the system would have 

 been identical with that universally used at sea, and with 

 such a field in which to show its usefulness it could not 

 have failed to become universal on land, and that in a few 

 years. Instead of this, after more than a century, it is still 

 (1899) soliciting clients. 



While it cannot be questioned that the French ought 

 to have seen that their system was not only academically 

 beautiful but also practically acceptable before they offered 



