The Indianapolis journal. [volume] (Indianapolis [Ind.]) 1867-1904, 1898-10-30

train of short wave length that passes
through the object, producing the A-oent-
gen effect. The more violent, abrupt and
irregular the hedge-fring. the more ahund-
ant will be these constituents or short
wave-length.
A rare combination of magnificent scien-
tific discovery and absurd application is
the ultraviolet light telegraph OF Prof
Zickler, of Brunn. A powerful arc lamp is
used as transmitter, with glass screen to
produce dot and dash flashes of the ultra
violet beam, and the remarkable result is
the perfection of the receiver, so that the
ultra yiOlet beam not only provokes dis
charge when 1t falls on the cathode OF
strained air gap. as was shown by Hertz:
but that this influence of the short ana
easily absorbed ultraviolet light is extended
to so great q distance as $50 feet
Failure of sound signals at sea has en-
phasized the Importance of much-neglect-
ed field of research An English investi-
gator. Rev. ]. NJ Bacon. has begun work in
this field along lines with special scientific
equipment, including an ear trumpet-hav-
ing a two-foot paraboloidal receiver-that
aids the ear as much as great telescope
aids the eye, an instrument for winnowing
out particular note as a prism separates
out given color, pipe that can be regu-
lated so that it can only just speak In one
condition of the atmosphere. and large
membrane that picks up sound with all the
subtilty of the human ear and likewise
registers the actual intensity. The sys-
tematic experiments commenced by Mr..
Bacon and his colleagues are being carried
out IN the air above as well as on land ana
sea- The most notable results thus far are
the differences in the sound-carrying power
or the atmosphere as observed from Dal-
LOOM a trip over London some years ago,
during wet period, having been ATTENDED
with street noises of indescriDabe harsh
ness and intensity, while a like trip TINS
year at the same season showed only an in
passage, at a higher elevation, but under
different conditions found the air filled
being easily detected at a mile and half
above. Even more curious is the hooking
of the echo from the empty air aloft, which
can always be caught, although on one OF
the six ascents no return of the voice from
the earth could be heard. The difference in
the sounds Of whistles and guns on different
the conditions of the atmospheric ocean
seem far more diverse than those of the
ever-changeful ocean of water.
Simple as ingenious is the idea of Pro-
copovitch, Polish mathematician, of using
the fingers as an aid in teaching and prac-.
ticing multiplication. Discarding the easily
multiplied to 5, he begins with 6, number
ing the thumbs of each hand and the
fingers in order up to 10 for the little finger.
To multiply any two numbers from to 10,
he places end to end the fingers representing
fingers of both hands toward the thumbs,
including both the two fingers pressed to-
gether and the thumbs, the sum being the
tens of his product and for the units he
multlphes the remaining fingers of the left
hand by those of the right hand. In multi
plying by g. it will be seen that the rule
gives but two tens. but the remaining four
fingers of each hand multiplied together
make 16 units. giving the correct result
when added to the two tens, or 90 Larger
numbers can be similarly multiplied, the
simplest method in the case of II to Is being
to number the thumb IL. the forefnger r.
and so on, when the fingers above the ones
placed together, including these, will give
the tens as before, while the units are diff
ferently found, the same fingers of each
hand giving the tens being multiplied by
those of the other. and finally 100 is added
to the tens and units thus obtained. Thus,
to multiply II by 13 the forefinger of one
hand and middle finger of the other would
be placed together, giving tens (5O) and
units, which added to 100 make 1856. For
numbers between 16 and 20 the thumb is to
be numbered 16 and the little finger 20, and
the fingers placed together added to those
above Will give the number of tWentieS, the
fingers below on one hand being multiplied
by those of the other for the units, as in the
series from to 10, and the whole increased
by 200 to give the correct result. The sys-
tenn can be extended indefinitely, the only
condition being that the two numbers to be
multiplied must always belong to~the same
series of five numbers.