The Baltimore County union. [volume] (Towsontown, Md.) 1865-1909, 1886-04-17
Correspondence Baltimore County Union.
SCIENTIFIC MISCELLANY.
INVISIBLE CLOUDS.


In the recent English tests of lighthouse lllu- |
minants was brought out the curious fact--of |
great practical as we'll scientific interest-that |
remarkable changes in the transparency OF the air
occur without any visible haze or mist Invisible
clouds seemed to float by, obscuring the lights for
time; and it sometimes happened that while
the distant French lights showed with undated
briiancy the experimental lights only mile
and a quarter away had lost one-fourth to one
third their power.
VARIATIONS IN GRANITE.
Prof. Vinchell's comparative trials of the gran
ties of New England and Minnesota have shown
some surprising differences in strength. Two
inch unpublished cubes taken, and, crushed
between wooden cushions, the average strength OF
Minnesota granite was found to be 81 1922 pounds,
of 23,2lS pounds per square inch crushed be-
tween steel plates, the average strength was lO4-
500 pounds, or 27,200 pounds to the square inch
of surface like number of specimens of New
England granite gave average strength of 3d.
1856 pounds, or IA, 759 pounds to the square inch
GIANT TREES OF AUSTRALIA
Evidence of the decay of forests in Australia is
found in the present existence of few trees far
exceeding in size any of those about them, and
supposed to be survivors of a departed race OF
giants A tree twenty-five feet in circumference
at a height of thirty feet above the ground was
described at a late meeting of the Royal Society
of New South Wales.
AN METEOROLOGICAL GARDEN.
An exhibition is projected at Berlin to show
the races of men and their habits as animals are
shown in geological gardens. In the exhibition
it is intended that representatives of various races
shall permanently reside, while of such races as
cannot stand the cold of the climate representa-
tives will be brought to Germany to reside during
the summer. museum of objects pertaining to
the different races will be established in connec-
ton. An attempt once made at the London
CRYSTAL Palace to represent various people and
Of ;vipo hu Of m
was never carried very far.
PLAQUES OF MICE.
At intervals of a few years, the Brazilian colony
of Lourenco suffers from remarkable visitation
of field mice, the latest of which, in 1876 has just
been described by Dr. Fl. Won hiring. These
creatures ordinarily not numerous, suddenly ap-
peared in enormous numbers, and in a few days
destroyed the fields of corn, potatoes, clover, oats
barley, gourds, pumpkins and even weeds, actual
ly damaging houses to considerable extent and
running furniture and clothing. The periodical
occurrence of these plaques seems to be due to
the chief food-supply of the mice, the seeds OF a
bamboo grass, which at regular intervals OF SIX to
thirty years natures a large territory and
then disappears. The feld-mice Increase SO
rapidly that, if all the conditions which keep
them in check were removed, single pair would
bear a progeny of q, 600 individuals in single
summer, and every living thing upon the earth
would be consumed in half dozen years.
HOW CHILDREN GROW.
remarkable physiological discovery has been
made by Rev. Mailing Hansen, principal OF the
Danish Institution for the Deaf and Dumb. Dur
ing period of three years he has made frequent
careful measurements and weghings of the l3O
children under his charge, and has reached the
conclusion that the body does not increase evenly
in bulk and height throughout the year, but that
during some months the child accumulates bulk
and remains stationary in height, while at an
other time there is growth in stature with com
parativey little increase in weight. These re-
suits are confirmed by similar experiments in
several smaller institutions in Denmark.
LIGHTING POWER OF COAL.
Franklin Instit te tests indicate that one pound
of coal burned under good boiler yields light
of about 90 candles by the incondescent electric
system. The same weight of coal gives from the
naked arc light about 15S candles, only SO can
dies being ordinarily available on account OF the
shading of arc lights. The gas from one pound
of bituminous coal yields from IA to II candles.
The greater economy of fuel in electric lighting
is offset by the increased expense for machinery
and attention.
MIsCELLANEoUs
1t is suggested that ball dresses may be render
ed safe from fire by accident by impregnation
with a twenty-five per cent. solution OF tungstate
of soda, which Injuries neither fabric nor color.
German metallurgist has introduced an ap-
paratus for pumping molten lead by steam pres
sure.
The discovery of hitherto unknown lake in
the Persian desert announced at a late meet
ing of the Vienna Geographical Society. 1t is at
least twenty five miles long, and from Moham-
medan evidence appears to have dried up after a
previous existence, and to have again filled up al
quite recent date.
A dictionary giving scientific and technical
terms in all languages is projected by Prof. Vii
anova, and is endorsed by the International Geo.
logical Congress.
Two French investigators have found that the
germs of fermentation are not destroyed per-
ceptibly affected by pressure of 800 to 400 at
mospheres continued for several days.
Recent German researches show that the puri-
fcation of natural waters is effected almost wholly
.hz nlant and animal agencies; the chemical ac-
ton of ozone, peroxide of hydrogen and atmos-
pheric oxygen exerting but a feeble influence.
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