llustrations.

VI. METEOROLOGY.--Climatic Changes in the Southern Hemisphere.
--By C.A.M. TABER.--Causes of the climatic changes the
southern hemisphere has undergone.

VII. MILITARY TACTICS.--The System of Military Dove Cotes in
Europe.--Continuation of this paper, treating of the pigeon service
in France, Germany, and Italy.

VIII. NAVAL ENGINEERING.--The Isle of Man Twin Screw
Steamer Tynwald.--A high speed steamer, with a steady sea-going
speed of between 18 and 19 knots.--2 illustrations.

IX. TECHNOLOGY.--Ammonia.--The manufacture of ammoniacal
gas for technical uses.--Full details of its production.

Musical Instruments.--Their construction and capabilities.--By
A.J. HIPKINS.--Second installment of this highly interesting
series of lectures treating of different kinds of instruments.

Note on Refrigerating Apparatus.

Sheet Glass from Molten Metal.--The method of making sheets
of glass from the molten material and manufacture of metal plates
by the same method.

X. VETERINARY SCIENCE.--Historical Development of the
Horseshoe.--By District Veterinarian ZIPPELIUS.--Very curious
investigation of the development of the horseshoe.--22 illustrations.

* * * * *

THE PRODUCTION OF HYDROGEN AND OXYGEN THROUGH THE ELECTROLYSIS OF
WATER.

All attempts to prepare gaseous fluids industrially were premature as
long as there were no means of carrying them under a sufficiently
diminished volume. For a few years past, the trade has been delivering
steel cylinders that permit of storing, without the least danger, a
gas under a pressure of from 120 to 200 atmospheres. The problem of
delivery without pipe laying having been sufficiently solved, that of
the industrial production of gases could be confronted in its turn.
Liquefied sulphurous acid, chloride of methyl, and carbonic acid have
been successively delivered, to commerce. The carbonic acid is now
being used right along in laboratories for the production of an
intense coldness, through its expansion. Oxygen and nitrogen, prepared
by chemical processes, soon followed, and now the industrial
electrolysis of water is about to permit of the delivery, in the same
manner, of very pure oxygen and hydrogen at a price within one's
reach.

Before describing the processes employed in this preparation, we must
answer a question tha