THE YARD, PENDULUM, AND METRE. 43J 



on the time of its vibration ; as if the 86,4ooth part of a 

 (}ay which we call a second of time were not as definite 

 and as invariable a quantity as the ioo,oooth part which, 

 in their rage for decimalization, they proposed to call 

 one ; and as if they might not have fixed on a pendulum 

 vibrating 100,000 times in a day (which would have given 

 a very near approach to our yard). But their stumbling- 

 block was the introduction of an extraneous element, 

 time, at all, into the subject : as if the length of the 

 day were not as much an invariable, universal, and 

 physical element as the dimensions of the earth or its 

 'gravitation. But in this they seem to have overlooked 

 the fact that their adoption of the quadrant of a meridian 

 for the base of their system does really admit this ex- 

 traneous element, time, into that system, though in a much 

 more insidious way. For the total bulk or mean radius 

 and the total mass or gravitating energy of the earth 

 remaining the same, the ellipticity of its meridians, and 

 therefore their absolute length, depends on the period 

 of its rotation or the length of the day. The same ob- 

 jection, to be sure, if it be one, would equally apply to 

 the adoption of the polar axis, or the equatorial diameter 

 of the earth ; and the only way to exclude all ideas of 

 time and force from a metrical system, and render it 

 purely metrical, i.e., dependent on geometrical magnitude 

 alone, would be to take for a fundamental unit the 

 radius, diameter, or circumference of a sphere, or the 

 side of a cube, equal in volume to that of the earth. 

 And perhaps were a tabula rasa made ; were the 

 ground totally unoccupied and the whole matter to do 



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