The National tribune., 1886-02-18
SCIENTIFIC CHAT.

The London Lancet says that children who are
allowed to go barefooted enjoy almost perfect inn
munity from the danger of cold ~ by accidental
chilling of the feet, and they altogether health
ier and happier than those who in obedience to
the usages OF social life. shoes and stockings.
BY means of simple chemical process a beau
tuui coiorlng OF yellow Is now given to marble
without any injurious effect upon the polish or
hardness of the stone. Neutral chloride of iron is
for this purpose dissolved in 90 per cent alco-
ho and after gently heating the marble to be
colOred, the solution in question is applied by
means of a brush. a sprinkler or by pouring the
strength of the solution being, of course proper
toned to the depth of the color desired and care
being requisite also in regard to the degree of tenn
perature. On the marble becoming completely
dry it is moistened with water exposed to moist
air, when the decomposition of the salt of iron
takes place in the upper strata and the process of
coloration is complete all that remains to be done
being to polish the surface if necessary or il NAV
be simply rubbed off with wet cloth. For light
tints very diluted solutions applied.
In an article on The Use of Oil at Sea- by
Lieut.. John p. Hodtch, II. n. r., the author says ::
" The results l have obtained these; Fish or
colza oil only is of any good; it does not matter
how dirty 1T is as long it is not thick. Parafine
is too thin paint oil too thick Running before q
gale naturally expends much more oil than laying
to, you have SO much more water to oil. Care
fully expended, one quart in three hours for run
ming one pint in four hours for laying to, will be
sufficient. The means L used was a canvas bag
(No. g., with large holes stabbed with a needle. /
have heard of a bundle Of oakum being saturated
with oil, and then put in coarse gunny bag which
think would admit of a thicker oil being used for
the time. The place for towing is undoubtedly
forward, not aft Whether in head-reachinsr oil
could be used successfully cannot say but doubt
1T. When running dead before the wind tow from
each cathead, and the ship is as safe as anything
can be at sea-"
"A device has been brought forward for protect
ing water pipes against freezing the arrangement
being based upon the fact that water in motion will
remain liquid at a lower temperature than water at
rest. One end of a copper rod, placed outside of
the building, is secured to bracket and the other
end Is attached to one arm of a weighted elbow
fhn 9TH .~f
rod which passes into the building and operates
valve In the water pipe. By means of turn buckles
the length of the copper rod can be adjusted so
that before the temperature reaches the point at
which there would be danger of the water in the
pipes freezing, the valve will be opened to allow
How of water; beyond this point the valve opening
Will increase and the flow become more rapid as
the cold becomes more intense, and as the temper
ature rises the valve is closed. This plan sets up
grows cold by the warmer water from the main.
Whether the valve be opened closed, the service
pipes are always in working order.
The discovery of a safe and efficient tanning
agent to take the place satisfactorily of the costly
hemlock bark has long been a desideratUm, not
withstandng the various substitutes which have
been brought forward. Recently considerable has
been said of the discovery made some time since by
an Arizona tanner of plant which carries large
proportion of tannin and which, when used in the
manufacture of leather, Is found to give extra
weight to the article produced. This plant is of
annual growth, indigenous to the deserts and dry
upiands, and is known as gonagra. 1t has a root
somewhat longer and more scraggy than the cuti-
waited beet, though resembling it in appearance,
impractical use has demonstrated its tanning prop
critics to be about three times great the ordi-
nary oak bark and that in all essentials it is superior
to such bark in the manufacture of leather. 1t has
now been in use for this purpose considerable
time, proving beyond question its superior adapted
ness, while in respect to cost, compared with
bark, 1t has immense advantage over the latter
Our principal observatories all work at spe-
cialties. At Harvard the relative magnitude of the
stars is the chief object of study; at Princeton
spectroscopy; at Allegany Observatory, the dark
part of the solar spectrum and the effect of the in
visible heat rays the earth: at the National OBJ
servatory, positions and orbits of satellites; at
Cincinnati. double stars; at Chicago, Jupters
face, and at Albany and Yale, perfeeting maps of
the heavens.