The Princeton union. [volume] (Princeton, Minn.) 1876-1976, 1881-02-17
POPULAR SCIENCE.

By the use Of sand and sulphur, with
an addition of 10 per cent. manganese,
the ancient black gloss Of the Venetians
is SO closely initiated, tits said, as todefy
detection.
To COLOR or dye small pieces Of ivory
black, wash we'll with an aqueous solu-
ton Of neutral nitrate Of silver. Elk
pose to sunlight under glass until
black. Repeat, If necessary, until the
proper color is developed.
An inventor thinks he has solved the
problem of propelling boats in canals
and rivers by means Of ejecting water
from the boat. Unlike his pred
he makes use not Of large pipe, but Of
a great number of tubes with very small
outlets.
The distance between New York and
Philadelphia, in an air line, is 81 miles,
over a comparatively level country. In
paper before the Franklin Institute,
Mr.. w. Barnet LIE Van maintained that
an airline road could be constructed
between the two cities, on which trains
could make the distance in one hour,
and that the enterprise would pay. The
line he proposed would cross no roads at
grade, and would have but two curves, of
10000 feet radius each.
1HE tests Of the durability of steel
rails on the Great Northern line Of
England show that the hardest rails do
not wear the best. In one instance q
hard rail was worn away one-sixteenth
of an inch by q traffic amounting to
5,251 900 tons. A softer rail near by
was worn the same amount by 8,4O2, 900
tons. In another instance the total was
Is, 531 1000 tons for hard rail, and 3d.
O61, 900 for soft rail, the wear and tear
being the same-one-six part of
an inch. Analysis showed this last rail
to consist of SO. 475 per cent. of iron and
minute quantities Of carbon, phospho-
rus, silicon, manganese, sulphur and
copper.
ATTEMPT has been made to propel
boats on canals and rivers by conduct
ing a column of water through pipe
and ejecting it forcibly at the stern, but
it did not prove successful. An English
man now claims to have got over the
difficulty by showing that ''the force ex-
erted by one fluid pouring into or against
another depends on the contact Of sur
faces, and not on the sectional area Of
the flowing mass, after the flowing mass
be once set in notion" Instead, there
fore, of tubes with large orifces, he
makes use Of tubes with narrow outlets,
mere slit, AID thus obtains large
superficial contact by ejecting water
through series Of narrow openings.
WHmEDr. Charles Roberts, in paper
on the hereditary transmission of physi-
cal and mental qualities, is at loss to
say how "vigor' may be utilized, he
makes bold dash at the solution Of the
problem. He is very decidedly of the
opinion that persons living under very
similar conditions OF life should not
marry. "a literary man should not
marry literary woman, nor tailor a
seamstress; and the rule should apply to
persons of the same temperament and
physiques. The immense trouble, so to
speak, which nature has taken to secure
Decentralization in the lower races Of
animals and plants should guide man in
his selection of partner" The evils
arising, or, better, transmitted or inten.
sifed, from the union Of persons under
like conditions of life are very similar t.
those which spring from the marriage Of
men and women closely related BY
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