The Madison journal., 1914-08-01

The maximum tides in these pipes did not ex-
ceed one-thousandth of an inch; but so perfect
the apparatus and so accurate the readings
by Professor Nicholson that all the variations In
the tides were accurately determined. Tides are
complex things. Their height varies with the
position and distance of both the sun and the
moon and. therefore, is never the same two days
in succession.
Professor Michelsons experiments revealed 80
of these variations which corresponded almost
exactly with the variations obtained theoretically
by computing the variations in the attractive
forces exerted by the sun and the moon. The
practical correspondence of the actual height of
the tides with the theoretical height proved that
the earth through and through is as rigid as steel
and that II yields to inside forces perfectly
elastic body and not as a viscous mass.
This experiment reveals the imagination and
the striking originality of Professor Nicholson.
The first achievement to bring his name to the
attention of the scientific world was his accurate
determination of the velocity Of light, accom-
plished also after overcoming tremendous expert
mental difficulties Light is the fastest thing in
nature; It represents the absolute limit Of speed.
After four years Of work and study Professor
Nicholson announced that light travels with a
velocity of 1S6.330 miles per second. The maxi
mum error In this figure does not exceed one
fortietlI Of one per cent.
On the subject of spectrum analysis, Professor
Nicholson has devoted many of the best years of
means Of the spectroscope Every substance
when heated emits a characteristic light. BY
means of the spectroscope this light is analyzed
and the elements giving OF the light are thereby
revealed. The spectroscope has enabled SCI
entists to determine the elements in far distant
stars. II has made possible tremendously impor-
tant discoveries concerning the nature of atoms.
the minute particles Of which all matter is COM
posed.
The difficulties of spectrum analysis will be
realized when II is learned that a single atom of
sodium emits 500 000.0000 900 vibrations per Sec
ond Of two slightly different kinds of light. Pro-
fessor Nicholson engaged in spectrum
analysis very long before he improved the spec
troscope. calling the improved type an echelon
spectroscope. This wonderful machine divides
light into its various constituents and makes pos
sible their separate analysis
The echelon spectroscope uses a glass grating
"a piece of highly polished glass which is
ruled from $4,000 to 50000 straight equay-spaced
lines to the inch. To make these gratings Pro-
fessor Nicholson invented ruling engine that Is
the most accurately constructed mechanical de-
vice in the world. 1t is operated in a room the
temperature of which Is kept constant to within
one-hundredth of a degree.
To assist In analyzing the lines Of the spectrum
into their fundamental constituents. Professor
Nicholson invented the harmonic analyzer,"
machine as complicated and delicate The
linotype machine. BY its use an assistant can in
few minutes make calculations that would take
a skilled computer weeks to accomplish
Scientists have long endeavored to determine
the absolute motion of the earth through space.
It Is known that the earth swings around the. sun