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_Friction of Screws and Screw-presses._
An examination of the friction in screws having their threads of various
forms, has led M. Poncelet to this very important conclusion, namely,
that the friction in screws with square threads is to that of equal
screws with triangular threads, as 2.90 to 4.78, proving a very
important advantage of the former over the latter, relative to the loss
of power incurred in both by friction.--_Brande's Journal._
_Fulminating Powder._
According to M. Landgerbe, a mixture of two parts nitre, two parts
neutral carbonate of potash, one part of sulphur, and six parts of
common salt, all finely pulverized, makes a very powerful fulminating
powder. M. Landgerbe adopts the extraordinary error of supposing that
these preparations act with more force downwards than in any other
direction.--_Bull. Univ._
_Aurora Borealis._
An aurora borealis was seen from North End, Hampstead, near London, from
about seven o'clock until eleven, on the evening of Dec. 1. It generally
appeared as a light resembling twilight, but shifting about both to the
east and the west of north, and occasionally forming streams which
continued for several minutes, and extended from 30 to 40 degrees high.
The light on the horizon was not more than 12 or 15 degrees in
height.--_Brande's Journal._
_Paper Linen._
According to the Paris papers, a new invention, called _papier linge_,
has lately attracted much attention. It consists of a paper made closely
to resemble damask and other linen, not only to the eye, but even to the
touch. The articles are used for every purpose to which linen is
applicable, except those requiring much strength and durability. The
price is low, a napkin costs only five or six centimes (about a
halfpenny), and when dirty, they are taken back at half-price. A good
sized table-cloth sells for a franc, and a roll of paper with one or two
colours for papering rooms or for bed curtains, may be had for the same
price.
_Maturation of Wine._
M. de St. Vincent, of Havre, states, from his own experience of long
continuance, that when bottles containing wine are closed by tying a
piece of parchment or bladder over their mouths, instead of using corks
in the ordinary manner, the wine acquires, in a few weeks only, those
qualities which is only given by age in the ordinary way after many
years.--_Nouveau Jour, de Paris._
_Indications of Wholesomeness in Mushrooms._
Whenever a fungus is pleasant in flavour and odour, it may be considered
wholesome; if, on the contrary, it have an offensive smell, a bitter,
astringent, or styptic taste, or even if it leave an unpleasant flavour
in the mouth, it should not be considered fit for food. The colour,
figure, and texture of these vegetables do not afford any characters on
which we can safely rely; yet it may be remarked, that in colour, the
pure yellow, gold colour, bluish pale, dark or lustre brown, wine red,
or the violet, belong to many that are esculent; whilst the pale or
sulphur yellow, bright or blood red, and the greenish, belong to few but
the poisonous. The safe kinds have most frequently a compact, brittle
texture; the flesh is white; they grow more readily in open places, such
as dry pastures and waste lands, than in places humid or shaded by wood.
In general, those should be suspected which grow in caverns and
subterranean passages, on animal matter undergoing putrefaction, as well
as those whose flesh is soft or watery.--_Brande's Journal._
_Zoological Society._
Dr. Brookes, in his address to the recent anniversary meeting of the
Zoological Society, stated that the _Museum_ already contains 600
species of mammalia, 4,000 birds, 1,000 reptiles and fishes, 1,000
testacea and Crustacea, and 30,000 insects. During the last seven
months, the _Gardens_ and Museum have been visited by upwards of 30,000
persons. The vivarium contains upwards of 430 living quadrupeds and
birds. The expenses of the past year have been 10,000 l., partly
contributed by the admission of the public, and still more largely by
the members of the Society, who already exceed 1,200 in number. These
are gratifying facts to every lover of natural history, as they serve to
indicate the progress of _zoology_ in this country--a study which it has
ever been our aim to identify with the pages of the MIRROR.
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