As the result of these various hydraulic operations, we have a perfectly formed cylinder closed at one end, and we now follow it into another department of the works, when its open end is once more brought in a furnace to a red heat.  The object of this is to make the metal soft while the shoulder and neck of the vessel are formed.  To accomplish this, the heated open end of the cylinder is laid horizontally upon a kind of semicircular cradle, and is held there by tongs handled by two men.  Another workman places over the open end a die 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.]