The citizen. (Frederick City, Md.) 1895-1923, 1897-03-05
written for the oitizen.)

cement, of Continental origin, for
which marvellous properties are
claimed. The material is called "pet-
rifite," and is flour like substance
understood to be composed of pecul-
lar kind of limestone mixed with
chemical matter. Like Portland &C.
ment, it can be used for binding to-
gether gravel and sand. The great
advantage claimed, however, is that
unlike other cements, it binds earth,
clay, lime, peat, pottery, glass, coal,
vegetable or animal fiber, sawdust,
and evidently about every other sub
stance. 1t hardens in twenty-four
hours without the aid of heat or pres
sure. 1t makes sand stone from sand,
incombustible hard wood from saw
dust, beautiful marble from dust, aud
an endless variety of materials for use
full and ornamental purposes.
The two gases commonly met with
in the mines are firedamp and black
damp, the former being explosive
when mixed with air, while the latter
extingulshes the flame. DR.. j. S.
Haldane, of the University of Oxford,
states that until recently blackdamp
was supposed to be carbonic acid, but
more complete analysis 10y himself and
Mr.. Atkinson, u mining inspector,
have shown that it is Il mixture of
about So parts of nitrogen and II
parts of carbonic acid. Its compost
ton varies but little in different parts
of the British Isles. The danger from
blackdamp is not due to It's calDonlc
acid, out to the excessive dilution by
the mixed gases of the oxygen of the
air.
No effort is being spared to make
the next meeting of the British Associa-
ton for the Advancement of Science,
to be held at Toronto in August, one
OF the most important scientific events
of the century. Grants of nearly $780,
600 aud literal concessions from steam
ship ana railway companies have been
secured. The American Association
and many foreign men of science are
invited To attend.
X y
The December and August heights
of mulberry tree have been found to
differ as much a03l inches, weigh
of 80 pounds failing in December to
lower one branch to its summer posi-
ton.
The new method of photography in
c0lors which has excited so much in
terest in London is an improvement
by Nj. VIliedleu-C hassagne, of Paris,
OF u process originally suggested by
DIR. Adrian Dansac. While the details
are being kept secret, it is known that
four separate solutions are used. One
of these is employed tor treating gea-
tine plates, on which the negative is
developed and fixed i'll the ordinary
manner, and from which an ordinary
appearing positive is printed. The
positive is washed successfully with
other solutions-which are colored
blue, green and red-when it takes up
the appropriate colors in appropriate
parts. In experiments by Sir II.
Trueman, Secretary of the Society of
Arts, pictures were made to take on
remarkably correct coloring, but not
withstanding these results Capt w. lie
w. Abney, the well known photo
graphic authority, expresses himself as
still not wholly convinced that so i'm
probable discovery as is claimed has
Ueen made. Captain Abney adds:
''SOme few years ago pow der process
was seen by Mr.. e. " Boys, in which
three colored powders selectively adj
hered to the surface of the paper. The
paper was prepared with some gluti-
nous substance and bi-chro IN "a e
of potash, and remained more or
less Iacky according to the amount
of exposure to light it had re-
ceived. These three powders-a red, a
green, and a blue, believe-if applied
in certain order, adhered to the print,
and gave approximately correct re-
suits Of color, though no SPECIAL mega
tive was required Whether this new
process depends on any similar grounds,
1t is hard to say at present.
various mineral mixtures by melted
lead in the process of two Swedish met
talurgists. Olm and Loftrand, and this
method is claimed to be SO effective
that even very poor ores are made to
yield a profit. The ores are simply
placed in hath of melted lead kept as
Tree as possible from contact with the
air. To gold ores containing little or
no bismuth, enough of the latter is
added to reduce the melting point of
the alloy as far as possible, thus lessen
ing oxidation and loss of metal.
The rapid rise of the land about Hud-
son Bay is said to be the most remark
able gradual upheaval of an extensive
region ever known. Driftwood-covered
beaches are now 20 to so or 20 feet
above the water, new islands have ap-
peared, and many channels and all the
old harbors have become too shallow
for ships. At the present rate, this
shallow bay will disappear in few
centuries. adding vast area of dry
land or salt marsh to British territory
In America.
Inc erosion OF the earth's exposed
portions assumes rather serious impor.
lance when we are told, as in DIR. John
Murray's latest lecture, that the CONT
nents will entirely disappear in about
5000 years If the present rate of wash
ing away continues. The average height
of the continents above sea-level is low
about 275 feet. The average depth of
the sea is something like $4,000 feet,