i88 3 .] 
575 
The Velocity of Light. 
Velocity of Light, metres per second. 
Fizeau ... 314,262,944 
Aberration and 
Parallax . 308,000,000 
Foucault ... 298,500,000 
Ratio of Ele&ric Units. 
Weber ... 310,740,000 
Maxwell... 288,000,000 
Thomsen . 282,000,000 
To which the results of more recent experiments and 
determinations of parallax might be added ; there is plenty 
of choice within certain limits. 
Clerk Maxwell made the ohm 1^28*8 of V, or, without 
being aware of it, as the mass of water-stuff is to that of air 
in the atmosphere, or the mass of salt to that of water in 
the sea. 
The first determination of the ohm was confusing. “ A 
body,” “ which in one second travels along a meridian from 
the pole to the equator, would have a velocity which on the 
eledtro-magnetic system is professedly represented by an 
ohm,” the distance from pole to equator being “ professedly ” 
“ 10 million metres, or 10,000 kilometres.” Maxwell said 
“ professedly,” “ because velocity and distance may not be 
quite correct.” 
The meridian of Paris has been found to differ, the equator 
is no circle, and the shape of the earth and the distribution 
of gravity is not without farther complications; but any 
meridian from pole to equator has its companion, and they 
have their pair ; the hemispheres are not of equal size ; the 
greatest difference of two meridian semicircles is about 
22,000 metres, and in the mean the circumference of the 
earth is about 40,000 kilometres. 
Strange would it have been if a resistance which expressed 
as a velocity “ professedly ” represented the distance from 
equator to pole should be overcome in exadtly a solar second, 
an arbitrary measure of time, sprung from the arbitrary 
division of a curve. For the division of the circle and the 
day are coeval ; the not quite concordant divisions were a 
convenient and mystic compromise between the decimal 
system for the rigid mathematical figure and the more or 
less duo-decimal system in the motions of the most observed 
heavenly masses with regard to our earth. 
The ohm is now determined 9413 kilometres, a velocity 
which would lead round the 40,000 kilometres in 4*248 secs. 
To the eledtric current moving from pole to equator and pole 
corresponds the magnet moving in transverse direction. 
The mass of vapour continually lifted into the air by the 
sun is 1^333x1^59*56 = 1^19833 of the mass of the sea, 
containing 1 7-29*78 of its weight in salt, led about by the 
