New-York tribune. [volume] (New York [N.Y.]) 1866-1924, 1878-09-21
SCIENCE I. FOR THE PEOPLE.

SCIENCE FOR THE PEOPLE.
PLATINUM PIcTUREs.-It is well known 10
ehemists that metallic platinum in all it's states mss-
awe and molecular unchanged or unaltered by atmos
pheric influences II is also well known that platinum
in finely divided state has intensely black Color
Now II picture be produced paper or other suitable
substance in which the dark portions and shades are
formed by this black finely divided metal 1t is evident
30 far as this metallic pigment itself 10 concerned that
the picture is perfectly permanent and unateraDle
The object the platinum to produce pictures
in which this result Is obtained The reacuoh
upon which the process is based is one discovered Dy
Mr.. W. Willis, IT,, some years ago. He found that not
solution Of ferrous oXalate in pOtassc oxaate Instantly
reduced platinum to the metallic state from its chic
rides and other salts The simple form the process now
takes may be briefly indicated as follows; Paper 10
coated with mixture Of aqueous solutions OF IerHo
oxaate and potassc chlOroplanite then dried ana e1
posed TO light under anegative. After 1t mas had
sufficient exposure it is hoated hot aqueous solution
containing potassc oxalate and salt Of platinum This
solution instantly develops the picture which Is then
washed in two solutions to remove the chemical
salts adherng to the paper Nhen aIieo aS pb LS
terest the fact that II is the first 10 which platinum
IN the metallic state has been made use OF as pigment
and that il ia the first phOtO-chemical process giving
permanent results of any practical value in which the
particles sGd 0 a@Cns IKE Ss Of he paper
which they printed and do not depend for their ad-
D'-''9 1'''N--'
BEST BATS FOR INsECTs.-M. E. G. Car
rere has lately been trying number Of experiments on
the best bats for insect traps and gives an account OF
them in the ReVus HOrtieOle. number OF glass NY
traps filed with different liquids sweet and sour, we're
placed under fruit trees subject to the attacks OF
flies and other insects. The traps were baited with
honey weak wine and water, Eeer and water, vinegar
and water, pure beer, pure wine, crushed pears ana
water aud other liquids then the victims were counted
after the traps had been exposed for three weeks WIN
the following results The trap containing beer and water
stood at head and contained $50 flies and other IN
sects pure beer stood next, with 63l the crushed
pears weak wine and pure wine coming next, pure
honey being at the bottom OF the POLL with only seven
teen sufferers doubt the OdOr Of the beer and water
which was i'm strong state of fermentation had great
deal to do with attracting the insects
THE EXTINCTION OF THE MAMM0TH.-Read-
ers of THE TRIBUNE will remember recent valuable
article on the mammoth by Professor Alex. Winchen.
At the meeting Of the British Association Mr. HOwarth
read paper on the difficulties surrounding the extnc-
tOn Of this huge elephant in Siberia One OF the theories
hitherto propOunded to account for its sudden dap
pearance he said that 1t lived in the central parts
of Central Asia, and that the careasses wer ioated
down the large rivers in that territory to sites
where the remains were now found. The examination
Of the stomach however, showed that the mammoth
lived on larch birch trees growing at the verge OF
woods near which the remains Of the animals were
found, aud their position showed thdG tuey nhu
wandered far when they we're entOmbed After looking
at the problem from every SIDE he had to the con-
eusOn that there had been sudden and violent change
Of climate in Siberia, which had frozen the previously
soft ground and had also preserved tie mammoth as in
8 huge meat safe. Although the mammoth had even
originally lived in the place where he was now found, 1t
was impossible that he could live there now, owing TO
the absence in that part Of the food which would be
necessary TO sustain him Such trees he used to live
on only found about 500 miles from the spot
larry that followed from tins theory was. that some
thing similar must be p9stuateu WIZ regap6 70 oHes
found Siberia precisely similar to those in which
America and precisely the same as those in the Great
Lakes, where the mammoth itself was found, ana II
could not therefore. be doubted that the mammoth
lived In Europe and America with the same food and
surroundings as It did In Siberia.
A SUBSTITUTE FOR WHITE LEAD.-A substi-
tute for white lead as the "body" Of paints has long
been desderatum Various substances have been tried
but with only partial According to The English
Mechanic however Mr.. Griths, Of Liverpool has dis
covered really effective substitute. The new pigment
said have higher covering power than white lead
while IL superior in color and at the time is not
injurious to the workmen 1t is obtained by procpitat-
ing zinc chloride suphate by Of soluble sui
phde sOde. barrie and cacie suphides have all been
used the purpose but special precautions taken
70 prevent the precipitation with the white sphde OF
any iron that may present in the chloride Of zinc
transferred furnace where is calcned being care
fully stirred to bring all parts into contact with the air
While st hot It Is raked into watts OF cold water where
IL levigAed, and Is then subsequently dried, the
product being white pigment Of great beauty, which s
chemical composition s. IN o. but 1t varies slightly
according to tue duration OF the cacinaOn and the tenn
peratuTe larger proportion OF oxide being occasionally
present
OCEAN BEACH PLACER MINEs.-A descrip-
ton OF the black sand beach placer mines Of California
was given by Mr. Christy at lsto meeting Of the San
Francisco Academy OF Science. Where the metal IL
found there are alternating layers Of magnetic iron sand
aud Of common quartz sand upon the higher parts of
the beach while down. where the surf breaks the
sand becomes cOarser and fuller Of pebbles Layers OF
black sand are not nfrequenty found upon the top Of
tho partly dried undsturbed sand owing TO the light
scous material having been removed by the action Of
the wind As one digs down. layers alternate white
and black the thickness Of each varying from that of
knife edge to three and six inches At depth OF two to
q sort of clay sandstone and upon the "hard pan" is
usually the best paydrt found Some OF the higher lay
ers Of black sand quite rich, also Under the micro
scope the black sand shows itself TO be composed OF
less perfectly rounded grains OF magnetic oxide
of iron with q few silica grains and occasional frag
ments OF what appears to be garnet Mixed with the
sand is the gold which, under the microscope usually
ance The gold is invariably In the form OF OblonR
ellipea scales, which dOuby cOncave and usually
surrounded by thckened rim Another curious fact is
purity OF the gold which has been reported 10
have assayed from $50 to 053 ue and is said 70 be the
purest placer gold ever found in California.
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RELIGIOUS INTELLIGENCE.