common dry air with electricity from sparks or points. Afterward
Faraday showed that it could be made by holding a warm glass rod in
vapor of ether. Again he showed that it could be made by passing air
over bright phosphorus half immersed in water. Then Siemens modified
the electric process by inventing his well known ozone tube, which
consists of a wide glass tube coated with tinfoil on its outside, and
holding within it a smaller glass tube coated with tinfoil on its
surface. When a current of dry air or oxygen was passed in current
between these two tubes, and the electric spark from a Ruhmkorf coil
was discharged by the terminal wires connected with tinfoil surfaces,
ozone was freely produced, and this was no doubt the best method, for
by means of a double-acting hand bellows currents of ozone could be
driven over very freely. One of these tubes with hand bellows
attached, which I have had in use for twenty-four years, is before the
meeting, and answers as well as ever. The practical difficulty lies in
the requirement of a battery, a large coil, and a separate bellows as
well as the tube.

My dear and most distinguished friend, the late Professor Polli, of
Milan, tried to overcome the difficulties arising from the use of the
coil by making ozone chemically, namely, by the decomposition of
permanganate of potassa with strong sulphuric acid. He placed the
permanganate in glass vessels, moistened it gradually with the acid,
and then allowed the ozone, which is formed, to diffuse into the air.
In this way he endeavored, as I had done, to purify the air of rooms,
especially those vitiated by the breaths of many people. When he
visited me, not very long before his death, he was enthusiastic as to
the success that must attend the utilization of ozone for
purification, and when I expressed a practical doubt, he rallied me by
saying I must not desert my own child. At the theater La Scala, on the
occasion of an unusually full attendance, Polli collected the
condensible part of the exhaled organic matter, by means of a large
glass bell filled with ice and placed over the circular opening in the
roof, which corresponds with the large central light. The deposit on
this bell was liquid and had a mouldy smell; was for some few days
limpid, but then became very thick and had a nauseous odor. When mixed
with a solution of one part glucose to four parts of water, and kept
at a temperature of from 20 deg. to 24 deg. C., this liquid un