The Portland daily press. [volume] (Portland, Me.) 1862-1921, 1881-09-12
A New Radiomoter.
Invented by Prof Carmichael OF Bowdoin

At the meeting of the American Ae7ociation
for the advancement of Science, held in Gin
cinnati, Prof Carmichael, of Bowdoin College,
described a new Radiometer which he had in
vented. Mr.. Carmichael exhibited an instru-
ment which was quite simple in construction.
1t consisted of two balls accurately balanced
upon pivot passing through the center OF
rod which connected them. The center OF
gravity could be raised by means of an adjust
able ball upon vertical wire at the balancing
point. Radiated heat from a lighted candle,
near at hand, disturbed the equilibrium of the
bulbs and produced motion which was util
ized ON the new Radiomoter, constructed upon
the came principle, of which was utilized on
illustration. The Radiomotor was described
in detail and was serted to be the smaliest
and met su .ceptible instrument for utilizing
radiated heat and light fs means Oh motion.
He said that he had already made use Oh tnis
instrument in the winding OF CLOCK, ana IL
constructed on a larger Gale could be used Tor
purposes requiring a continuous power. he
also remarked that full sunlight falling on a
surface ten feet square is equivalent to the en-
ergy of twenty-five horse power engine,
There is no machine of which even thous'
andth of this quantity can be utilized in the
produ ction of motion purposes. This little IN
strument is step toward gaining this object.
Mr. Carmichael also read paper describing
ga New Differential Thermometer" simple
and curious instrument, which is destined to
revolutionize the old methods OF ~esting rela-
tive temperature. He exhibited the instru-
ment and explained the details OF its constlu-
struction and its use.
The instrument is designed as convenient,
simple and economical substitute for the Gus
tomary thermo-pie, and the mirror galyant
meier in mes s7uring and exhibiting to an audi
ence small amounts of radiant heat The in
strument consists of two gsss bulbs OF the size
of a walnut, connected by means of tube no
larger than a quill, which, in peculiar man
ner is SO bent in its central portion that it
there describes semi-circle at. right angles TO
the axis connecting the bulbs; and through the
centre of which semi circle the axis passeG. A
knife edge is placed on the axis, and by means
of this, the bulbs are supported and permitted
to revolve upon the common axis.
The glass part of the instrument is so bal
anced on the knife edge that it is in neutral
equilibrium. A drop of alcohol is lnclosed In
the tube forming the semi-circie. The DulDs,
which are covered with lamp black, in. order
that they may absorb heat more readily are
protected by two brass cones with their mouths
facing outward. So long as the two bulbs are
of the same temperature, the drop OF alcohol
and consequently the instrument remains at
rest. AS soon as one bulb is exposed to radiant
heat the drop is set in motion towards the 9th
er bulb, and consequently causes the instru-
ment to partly revolve. A cold object brought
into the neighborhood would have the oppo-
site effect as would also radiant heat when
admitted to the other bulb. To render move
ments of the instrument conspicuous long
glass filament OF arm is attached to it, upon
the end OF which white disc is placed. By
the movement of this disc up and down, as 1t
is easily seen by the audience, the intensity OF
the heat or cold is measured. To indicate the
delicacy OF the instrument it was shown that
even the heat radiating from the hand, held
short distance from the opening OF the cone
produced a marked movement of the white
disc 1t was stated by Mr.. Carmichael that in
colder weather the heat coming from hand
held at distance of five feet could readily be
measured and the heat of candle at still
greater distance.
Professor Carmichael was loudly applauded
as he finished his explanation, and, Aindeed,
the interest Of the audience was manifest by
the wrapt attention with which it listened to
his talk throughout.