The Baltimore County union. [volume] (Towsontown, Md.) 1865-1909, 1903-05-23
Correspondence Baltimore County linton.
SCIENTIFIC MIS- CELLANY.

cckftHttAcftCc ~fsN~0"
SCIENTIFIC MIS- CELLANY.
New Dust Fieures-White Light for the |
sDark'i Room-A Promising Heater
An Imitation Rivera Fast Growing
Fish-The Best Foods-The Secret OF
Magic Mirrors-Varieties OF BecQuerel
Rays-Electric Billiards.
Curious figures are obtained by DR.. W. Rus
sell when magnesia dust or other fine powder Is
sprinkled over plate of glass, copper, eDonlte
cardboard or other material, the plate being
about 12oC. warmer than the air. The best re-
suits are obtained when the dust gently settles
over the plate during cooling. The figures vary
with the shape of the plate, usually showing
radiations from the angles. and they are affected
also by any neighboring object, such as an up
right pin at the edge of the plate, or piece Of
glass over it. After week or fortnight the
dust figures become so adherent that they can
be brushed gently without injury.
Non-actinic white light, first made known by
French photographer some years ago, is pro-
duced by altering sunlight through colorless
solution of three parts of nickel chloride and
one part of cobalt chloride, ultraviolet rays
being absorbed by coating the containing vessel
with collodion mixed with sulphate of quinine
slightly calculated with sulphuric acid. Sensi-
ntive paper has been exposed to this filtered
white light for a week without change.
"a
The electric radiator of E. G. Rivers has
layer Of finely powdered retort carbon held be-
tween enamelled iron plates and kept in posi-
ton by asbestos cardboard. copper strip is
led in at the center, with another at each end,
and a continuous current is passed from the
center strip to the outer two. current of
eight amperes at 200 volts keeps heating sur
face of 25 square feet at an average temperature
of 190oF.
An experienced riieman has noticed that the
position or a target appears to change from
hour to hour during the day. In a range extend
ing to the north, the aim and sight correction
that will hit the bulls eye at noon will hit to the
left and above in the morning and to the right
and below in the afternoon.
-
Laboratory of River Hydraulics, with an
artificial river for studying the work of streams,
is novel feature of the Technical Institute of
Carsruke. The "river'' is a tank, with suitable
inlet and outlet, and simple mechanism for
varying the inclination. When the effect of the
current in any channel is to be investigated,
careful survey of portion of the real river is
first made. Then the tank is given the proper
slope, and the natural conditions are reproduced
on a small SCALE little bags of shot being used
to consolidate the sand of the banks and to rep
resent either the stones of faced embankment
or the boulders of a gravelly soil. The bottom
is covered with 2K inches of sand. In order
that only the stage of flow desired may produce
any effect upon the bed, the tank is provided
with means for carefully filling before the out
let is opened, and for emptying very slowly at
the end of the experiment.
"a
The Partisan idea of introducing electricity
into billiards is ingenious at least In the CEN
ter of the table is placed a plate of some
easily electrified substance, and the balls are of
compressed pitch, the cue being tipped with
chemicaly-prepared cork. The balls being in
fiuenced by the electrified plate, caroms are
difficult. The player finds exercise for greater
skill than ever, it is claimed, and the new diff
culties add zest to the game.
4F4
Observations on the growth of fishes are
sought by returning to the water healthy speci-
mems that have been weighed and tagged.
Among the fishes retaken in English waters last
year were a sea trout that had increased from 8
pounds to in one year, salmon that had
risen from 10 pounds to q in eighteen months,
and male salmon whose weight seems to have
shown an extraordinary and astonishing growth
from 10 to SO pounds in thirty days.
80
The salinity of the oceans varies greatly in
different localities. Recent investigations have
shown that the surface of the Atlantic has two
large areas that are very salt. one north and one
,south of the equator, but that only one COM
parativey small salt area, south of the equator,
is to be found in the Pacific.
-.
For nutriment and digestiblity combined,
the herring is placed at the head of all animal
foods by Prof. MacFadyen, a London Royal In
stitution lecturer. The whiting is one of the
easily taken Care Rs the Sn sne
fatter salmon, mackerel and eel. Lean beef is
nearly as digestible as fish, much more so than
fstty mntton. The food value of beef-tea and
of oysters has been greatly over rated and fish
has no extra Importance for brain-workers on
account of its phosphorus, as there is no exper-
mental evidence to show that it contains more
phosphorus than other animal food. First
among the vegetable foods are to be placed the
pea, the bean and the lentil the last named
being among the most ancient forms of food.
~.
A perplexing mystery of few years ago was
the curious property of Japanese magic mir
rors which, as is well known, reflects upon
screen the designs engraved upon their backs,
although the polished rejecting faces are quite
plane and free from any visible figures. 1t is
now pretty well proven that the popularity is
due to unequal resistance to fexure during the
polishing process. A late experimental, Thomas
Thorp, has reproduced one of these mirrors in
bell-metal, using-wth much pressure-ordina-
ry methods of grinding and polishing instead of
the Japanese method of scraping with pressure,
and the reproduction is an improvement upon
the original Another mirror, made with care
to avoid fexure, was quite free from the magic
property.
~
The rays emitted by the radioactive metals
are found by Becquerel to be of more than one
kind. Those from uranium, which are of one
kind only, are charged with negative electricity,
and have high penetrative power; those from
polonium are charged with positive electricity,
and are easily absorbed and those from thorium
are of both kinds.
~
Medical authority has regarded suicide by
holding the breath as impossible, but late
Liverpool suicide seems to have accomplished
the feat.