112 
POPULAE SCIENCE EEYIEW. 
spores, which are supposed to be the life of the dust, and which lightness 
may be described as almost approaching volatility. There is, probably , an 
altitude of the maximum of activity for all localities as regards dust. It is so 
light that even that obtained in an ordinary house contains a large portion 
that refuses to sink when thrown upon water ; and, even when the vessel 
is placed beneath an air-pump, a large percentage floats. To him the activity 
of the dust taken from the top of the monument 134 feet high is something 
marvellous — this source so far removed from the busy streets — yet its organic 
matter contains what is capable of splitting up, in a short time, hundreds of 
times its own weight. 
Meteoric Bust in Snow. — This is a curious subject, but it has been very 
well followed out by Herr D. Huseman, who in the “Neues Jahrbuch fiir 
Pharmacie ” (September) gives an account of a reddish-coloured dust which 
fell along with snow in the Swiss canton Du Vaud in the winter of 1807. 
According to a calculation, made from experiments and observations con- 
ducted with care, the quantity of dust fallen over the entire surface of the 
canton amounted to about 1,500 tons. The author examined the dust, as 
well as the snow which had fallen simultaneously. The water yielded by 
the snow contained a considerable quantity of sulphate of lime and organic 
matter, both of which are absent in ordinary snow-water, at least in Switzer- 
land. The microscopical inspection of the dust proved it to contain minute 
particles of mica, felspar, quartz, and variously shaped organic matter. After 
having been dried at 100°, and ignited, the loss amounted to from 20’8 to 
even 24 per cent, for four different assays. The greater portion of this loss 
was due to the volatilisation of water, of crystallisation and constitution, but 
nitrogenous organic matter was also found to be present. Of the residue 
after ignition, about half was found to be soluble in hydrochloric acid. 
This solution, which was only qualitatively tested, contained peroxide of 
iron, lime, alumina, magnesia, and sulphuric acid j the portion insoluble in 
acid, having been fused with a mixture of potassa and soda, was found to 
contain, beside a large quantity of silica, also alumina, oxide of iron, and 
lime. The dust, when treated with an acid, gave ofl* carbonic acid largely. 
Gas and Gas-works. — A paper entitled “Instructions, Rules, and Regula- 
tions concerning the Use of Gas and the Inspection of Gas-works, Gas- 
meters, and Gas-pipes, ordered to be observed by the Communal Authorities 
of Karlsruhe” (Baden), which should be consulted by gas makers and 
engineers, will be found in the September number of the “Journal fiir Gas- 
beleuchtung.” 
Experiments in Sub-permanent Magnetism. — The following experiments 
are described in the “ Chemical News” of November 25. The object of the 
experiment is to produce, in a few minutes, what Dr. Tyndall has named sub- 
permanent magnetism ; and thus represent to a class quickly what is effected 
by the earth sloivly in soft iron lying in the magnetic meridian, and subject to 
molecular disturbance from percussion or other causes. The requisites for 
the experiment are — a block of cast iron (wrought iron might, perhaps, do) 
slightly magnetised, a bit of soft iron wire, a hammer, and a magnetic 
needle for testing the wire. Expt. 1. Lay the iron wire on the block, and 
hammer it lightly from end to end, for a few seconds. Presented to the 
needle, the wire will be found magnetised, showing distinctly strong north 
