the creation
of the modern amateur photographer, who can make lantern slides, and
the more general adoption of the optical lantern for the purposes of
demonstration and amusement, there has arisen a demand for the
limelight such as was never experienced before, and as the limelight
is dependent upon the two gases, hydrogen and oxygen, for its support,
these gases are now supplied in large quantities commercially. At
first the gas cylinders were made of wrought iron; they were cumbrous
and heavy, and the pressure of the inclosed gas was so low that a
receptacle to hold only ten feet was a most unwieldy concern. But
times have changed, and a cylinder of about the same size, but half
the weight, is now made to hold four times the quantity of gas at the
enormous initial pressure of 1,800 pounds on every square inch. This
means the pressure which an ordinary locomotive boiler has to
withstand multiplied by twelve. The change is due to improved methods
of manufacture and to the employment of mild steel of special quality
in lieu of the wrought iron previously employed. The cylinders are now
made without joint or seam, and the process of manufacture is most
interesting. A short time ago we had an opportunity of watching the
various necessary operations involved in making these cylinders at the
Birmingham works of Messrs. Taunton, Delamard & Co., by whose courtesy
we were enabled to make notes of the process.

[Illustration: FIG. 1.]

[Illustration: FIG. 2.]

Beginning with the raw material, we were shown a disk of metal like
that shown in Fig. 1, and measuring thirty inches in diameter and
three-quarters of an inch in thickness. From such a "blank" a cylinder
destined to hold 100 feet of compressed gas can be constructed, and
the first operation is to heat the "blank" in a furnace, and afterward
to stamp it into the cup-like form shown in Fig. 2. To all intents and
purposes this represents the end of a finished cylinder, but it is far
too bulky to form the end of one of the size indicated; indeed, it in
reality contains enough metal to make the entire vessel. By a series
of operations it is now heated and drawn out longer and longer, while
its thickness diminishes and its diameter grows less. These operations
are carried out by means of a number of hydraulic rams, which
regularly decrease in size. Fig. 3 roughly represents one of these
rams with the plunger ready to descend and force its way into the
partially formed red