ns and Halske, of Berlin, recently invited the members of
the Elektrotechnische Verein of that city to their works to witness
the demonstration of a series of experiments on alternating currents
under a pressure of 20,000 volts. In order to show that the desired
pressure was really _en evidence_, the high tension was conducted
through a pair of wires of only 0.2 mm. diameter to a battery of 200
100-volt incandescent lamps, all connected up in series. An ordinary
Siemens electric light cable was inserted, and broke down at a
pressure of some 15,000 volts.

At the end of the meeting a few experiments on the formation of the
arc under this enormous pressure were shown. The sparking distance
varied considerably, according to the shape of the electrodes. At
20,000 volts a spark jumped from a ball to a ball about 10
millimeters, while between two points a sparking distance of 30
millimeters, and sometimes even more, was reached. This arc is shown
half size in the accompanying engraving.

[Illustration: A 20,000 VOLT ALTERNATING ARC (half size).]

The arc which followed the jumping over of a spark made a loud humming
and clapping noise, and flapped about, being easily carried away by
the slightest draught. The arc could be drawn out horizontally to
something like 100 millimeters distance between the electrodes, and
even to a distance of 150 millimeters, when carbon pencils were used
as electrodes, but it always remained standing up in a point.
--_Electrical Engineer._

* * * * *

THE RELATION OF BACTERIA TO PRACTICAL SURGERY.[1]

[Footnote 1: The address in surgery delivered before the Medical
Society of the State of Pennsylvania, June 4, 1890.]

By JOHN B. ROBERTS, A.M., M.D., Professor of Surgery in the Woman's
Medical College and in the Philadelphia Polyclinic.

The revolution which has occurred in practical surgery since the
discovery of the relation of micro-organisms to the complications
occurring in wounds has caused me to select this subject for
discussion. Although many of my hearers are familiar with the germ
theory of disease, it is possible that it may interest some of them to
have put before them in a short address a few points in bacteriology
which are of value to the practical surgeon.

It must be remembered that the groups of symptoms which were formerly
classed under the heads "inflammatory fever," "symptomatic fever,"
"traumatic fever," "hectic fever," and