CVII
action. If a spark is passed through a mixture of two parts of
hydrogen and one part of oxygen water is formed (443); thus if in
a little cannon put on an insulator a mixture of two parts of hy
drogen and one part of oxygen are introduced and the cannon
is closed by a cork, by the disc of an electrophorus the two gases
may be caused to combine and their violent explosion will drive
out the cork.
§ 269. 8) The Leyden jars may be combined so as to form
an electric battery. 429. The greater the number of jars the
more powerful the effects will be.
§ 270. The effects usually are divided into: a) physiologi
cal, b) luminous, c) heating, a) mechanical, e) magnetic, and
f) chemical. As to a) If the two electricities of a Leyden jar
unite through the medium of our body, a violent shock is felt in
the elbow. This shock may be given to a large number of
persons simultaneously, if they form one chain by joining hands;
little animals may be killed this way. 429. The effects under b)
have already been mentioned, c) The electric spark is a source
of intense heat. Coal gas may be ignited by a person on an insu
lating stool placing one hand on the conductor of a machine and
presenting the other to the jet of gas issuing from a metallic
burner. Even a metal wire may be melted by an electrical
spark. d) As to the mechanical effects a piece of wood may be
smashed and a piece of glass or a card can be perforated by
such a spark, e) a steel bar or needle may be magnetised. f)
the action upon the chemical constituents of water has been al
ready mentioned. Besides that, if electricity issues through a
series of points from the conductor of a machine, a modification
of oxygen is produced, which is called ozone and which is re
cognised by a peculiar odour. Ozone may also be produced by
putting a piece of phosphorus into a little flask and pouring in
