Public ledger. [volume] (Memphis, Tenn.) 1865-1893, 1882-10-04
HOW FAST DOES LIGHT
TRAVEL!
Experiments About 10 be Made
to Determine the Question.
Cleveland lie der.

Important experiments are about to
be made at the East End by Professor
Albert A. Nicholson, under govern
ment auspices, to determine more
accurately than ever before the veloc-
ity of light. Mr.. Nicholson is a
young man who graduated from the
Naval Academy at Annapolis. Md, in
1873. He came to Cleveland in May
of this year, and is now connected
vita the Case School Of Applied Sci
ences.
After his graduation::he remained at
the Naval Academy in Annapolis and
undertook patient experiments to
determine how fast light travels. The
most accurate previous conclusions on
this point were those of NJ. Cornu,
made at the Observatory at Paris in
1874. The velocity of light according
to these experiments, was 300 400 Kill
ometres, or nearly 1864 miles, per
second. Mr.. Nicholson in his exper-
iments in 1879, arrived at a velocity
of 299, $40 kilometres. or l86,380 miles
per second.
While he was experimenting Pro-
lessor Simon Newcomb, of Washing
ton, superintendent of the Nautical
Almanac, visited Annapolis and inter-
ested himself in Mr.. Miohelson's op-
erations. Mr.. Newcomb did not be-
lieve the result obtained was as close
as possible, and with Mr.. Michelson's
assistance undertook experiments Of
his own at Washington. He arrived
at a conclusion slightly differing from
Mr.. Michelson's figures, but has not
yet published the results he obtained.
Later he repeated his operations and
obtained the same result as at first.
He then asked Mr.. Nicholson to re.
peat his experiments. The latter has
agreed to do so at Cleveland, and
preparations for the work are almost
complete.
The cost will be about $1,000, and
will be borne by the Baehe scientific
fund. The site Of the experiments
in the grounds of the Case School at
East End. Here two buildings have
been erected by Mr.. 4. P. ~Ingersoll,
the well known contractor and builder
of Logan street. The larger building
10 by 10 feet contains a small engine
and the chief apparatus. Two thous-
and feet west oft is q small building
containing a stationary mirror. The
buildings have been erected and the
apparatus will be ready for work in
about two weeks. The machinery
aud manner of the experiment are
quite complicated. In brief, however,
a ray OF sunlight is thrown upon a
slowly revolving mirror. whence it is
reflected upon the stationary mirror
1000 feet away, and from there re-
Aected back over the same path.
As the revolving mirror turns slowly
the returning ray is moved slowly to
one side. The velocity of the light is
measured by a calculation OF the va
rious distances from mirrors to mir
rors, angles, rapidity and distance Of
movement Of the revolving mirror,
distance Of movement of the returned
ray, etc. Professor Nicholson thinks
that when he gets at work be can con
clude his experiments and investiga-
ions il about three weeks. The
work will be closely watched by scien-
lists interested in that subject. The
velocity Of light has an important
bearing upon astronomical calcula
tons and the experiment will be one
Of considerable value. Professor
Nicholson, though a young man, has a
reputation as a careful, reliable and
conscientious investigator. His being
placed in charge Of the Department
Of Physics of Case School is eyi
dence that be is an accomplished
scientist.