LXVI PHILOSOPHICAL SOCIETY OF WASHINGTON. 
covered yard he could measure a cubic foot of it, and thus recover 
the standard of mass which we call a pound. ‘The recovery of our 
standard of time would be more difficult; but even that could be 
accomplished with an error not exceeding half a minute in a day. 
One way would be to perform Michelson’s modification of Foucault’s 
experiment for determining the velocity of light. Another way 
would be to make a Siemen’s mercury unit of electrical resistance, 
and then, either by the British Association method or by Lord 
Rayleigh’s modification of Lorenz’s method, find the velocity which 
measures its resistance in absolute units. Still another way would 
be to find the ratio of the electro-static and electro-magnetic units 
of electricity. Thus all the units now used in transacting the world’s 
business could be made to reappear, if not with scientific, at least 
with commercial accuracy, on the other side of an abyss of time and 
space before which the human mind shrinks back in dismay. The 
science of the eighteenth century sought to render itself immortal 
by basing its standard units upon the solid earth, but the science of 
the nineteenth century soars far beyond the solar system and con- 
nects its units with the ultimate atoms which constitute the universe 
itself. 
