ie of the form shown in Fig. 4, and while the cylinder is slowly
turned round in its cradle, two sledge hammers are brought down with
frequent blows upon the die, closing in the end of the cylinder, but
leaving a central hole as shown in Fig. 5. Further operations reduce
the opening still more until it is closed altogether, and a projection
is formed as shown at Fig. 6. This projection is now bored through,
and the cylinder is ready for testing.

[Illustration: FIG. 4.]

[Illustration: FIG. 5.]

[Illustration: FIG. 6.]

The cylinder is submitted to a water test, the liquid being forced in
until the gauge shows a pressure of two tons to the square inch.
Cylinders have been known to give way under this ordeal, but without
any dangerous consequences. The metal simply rips up, making a report
at the moment of fracture as loud as a gun. The wonderful strength of
the metal employed may be gauged by the circumstance that the walls of
the cylinder designed to hold 100 feet of gas are only five-sixteenths
of an inch in thickness.

During the manufacture of the cylinder, as we have already indicated,
much oil is used, and, so far as steel can be saturated with that
fluid--in the popular sense--the metal is in that state. It is
essential that this oil should be completely got rid of, and this is
carefully done before the cylinder is charged with gas. Previous to
such charging, the vessel has to be fitted with its valve. Of these
valves there are three kinds, known respectively as the Brin, the
Birmingham, and the Manchester. Each has its admirers, but we cannot
here discuss their individual merits.

The charging of the cylinder is brought about by a powerful pump
having three cylinders so arranged that the compressed contents of the
first cylinder are still further compressed in the second, and still
more highly in the third. The filling of a 100 ft. cylinder occupies
about half an hour.--_Photographic News_.

* * * * *

HISTORICAL DEVELOPMENT OF THE HORSESHOE.

BY DISTRICT VETERINARIAN ZIPPELIUS, OF WURTZBURG.

_Translated by S.E. Weber, V.S.[1]_

[Footnote 1: From _Theirarztliche Mittheilungen_, organ des
Vereins badischer Theirarzte, Karlsruhe, No. IV., April,
1891.--_Veterinary Archives._]

Kind, gentle steed, nobly standing,
Four shoes will I put on your feet,
Firm and good, that you'll be fleet,
That is Donar's hammer saying.

To