396 
POPULAR SCIENCE REVIEW. 
PHYSICS. 
Origin of Meteorites. — As there is no subject which has given rise to 
so much conjecture in the minds of physicists as that of the source of 
meteorites, every new hypothesis is examined with interest. Among the 
many speculations as to the cause of these curious bodies, not the least 
attractive is that which has lately been put forward by Dr. Eeichenbach, of 
Vienna. This savant believes in the existence of a cosmical powder or dust, 
which extends through aU space, and which sometimes becomes agglome- 
rated, so as to form large and small meteorites, which, at the time it readies 
the surface of the earth, is in the form of an impalpable powder. It is 
known that meteorites are composed chiefly of nickel, cobalt, iron, phos- 
phorus, &c., and as these are not common constituents of our soil, it has 
hitherto appeared impossible to refer the meteorites to a source in our earth ; 
but Dr. Eeichenbach shows that the dust which covers the tops of mountains, 
that have never been touched by the implements of the miner, contains 
nickel, cobalt, phosphorus, and magnesia in notable proportions. Hence 
his conclusion as to the origin of meteoric bodies. 
A useful Form of Magnesium Lanvp has just been devised in Paris. The 
objections to the previous forms are — 1st, the irregular dlummating power of 
the flame ; and^ 2nd, the occasional extinction of the light. To obviate 
these difficulties, !M. Matthieu Plessy employs a small hydrogen flame, in 
which the end of the magnesium wire is burnt. By these means an equable 
illumination is obtained, and the magnesium ^vire cannot cease to burn ; 
whilst the hydrogen flame being neutral, no injurious optical eftects are 
produced. 
Fadiaiion of Darh Fays of Heat. — Some of the most interesting experi- 
ments which have ever been made in the investigation of the manner in 
which heat is radiated, are those which Professor Tyndall lately displayed at 
the Eoyal Institution. The lecturer’s object was to show that after the rays 
of light proceeding from the electric points have been completely absorbed, 
the heat-rays still travel on, and appear to lose none of their intensity. The 
electric light was reflected by a concave mirror of about eight inches focus, 
and a cell of rock-salt, containing iodine in sulphide of carbon, was placed 
between the mirror and its focal point. By this means aU the hght was 
absorbed ; yet when objects were placed in the focus of the mirror, they 
instantly became inflamed. Wood painted black, when brought into the 
dark focus, emitted copious volumes of smoke, and was soon kindled. Paper, 
charcoal, mixtures of oxygen and hydrogen, zinc-foil, magnesium wire, and 
other metallic substances, were similarly affected. For a general expression 
of the phenomena thus produced. Professor TyndaU suggests the term 
calorescence. 
Connection betiveen Electric and Atmospheric Disturbances. — At the meeting 
of the Eoyal Society on Thursday, February 23rd, Admiral Fitzroy pointed 
out some very curious effects of atmospheric electricity upon the wires of 
telegraphs. It appears that at certain periods the electric wires become 
perceptibly affected ; and this, according to observation, cannot be attributed 
to any action of the batteries with which they are in contact. Whenever 
