which it could not be freely worked, to that peculiar plastic condition in which it is capable of being pulled, bent, blown, or cut into every conceivable shape without breaking or parting with its adhesiveness. The glass should be kept in this state all the time it is worked, which may vary from six to twenty-four hours.

Although the manual operations of fashioning various articles of flint-glass are varied almost indefinitely in their details, according to the particular form required, they are reducible, nevertheless, to a few simple processes, some of which may be illustrated by an account of the manner of producing a small bell-shaped jar. The implements of the glassblower are few and extremely simple. The most important one is an iron tube, open at both ends, from four to five feet in length, with a bore of from one-third of an inch to an inch in diameter.

A mass

of the soft glass is collected on one extremity of this tube or blow-pipe, by alternately dipping the end of the pipe in the glass and exposing it for a moment to the air, until a sufficient quantity is obtained. The pipe is then held in a perpendicular position for a few seconds, with the end to which the glass is attached downwards; and when the mass is sufficiently elongated, it is rolled on a smooth and flat iron plate, called the "marver,"* in order to give it a cylindrical form. The workman now blows strongly through the tube, to cause the lump of glass to be distended by its plasticity and the pressure of

* Corrupted from the French marbre. The English names of several implements used in glass-houses are clearly derived from their French

names.

the breath into a hollow globe (fig. 3). When a vessel of moderate size is required, it seldom happens that the globe is obtained sufficiently large and thin by a single blowing; and as the expanded glass

presently solidifies, it becomes necessary to soften it by the application of heat previous to the second blowing (fig. 4). The alternate heating and blowing are continued until the globe is obtained of a convenient size and thickness.

At this stage of the process, an assistant applies to the surface of the globe, at a place immediately opposite to that at which it is attached to the tube, a knob of soft glass on the end of a solid iron rod called the "punto" or "pontil," considerably smaller than the tube used for blowing. The two soft masses thus becoming firmly welded together, the first workman detaches the globe from the tube by touching its tubular neck either with a file or an iron rod just before wetted with cold water. After a crack has been thus produced, a smart stroke on the tube readily separates the globe, which must then be held by the punto.

Having once more softened the vessel by holding

it at the mouth of the furnace, the workman proceeds to expand the aperture left by the removal of the tube; for which purpose, his principal instrument is one resembling a large iron forceps, called a "procello," the two blades of which are connected

Fig. 5.

by an elastic bow, like those of a pair of sugar-tongs. With this instrument the workman, being seated on a stool provided with straight projecting arms, as shewn in fig. 5, enlarges or contracts the glass vessel as may be desirable,

running the pontil at the same

time on the arms of the stool. The superfluous glass is cut away with great facility by a large pair of scissors.

When the vessel is fully formed and become quite solid, it is detached from the punto in the same manner as it had previously been detached from the tube, and is immediately conveyed to the annealing arch to undergo a very gradual refrigeration, the reasons for which have already been adverted to.

The mode of fashioning a common wine-glass will also afford a good example of the ordinary manipulations of the glass-blower. A small bulb, of the form shewn in fig. 3, having been blown, its extremity is flattened by revolving it on the arms of the stool, against a small disc of iron, and an assistant applies to the flattened end a little lump of soft glass, which is elongated by the pro

Fig. 6.

cello so as to form the leg of the wine-glass (fig. 6). While this is being done, the assistant blows a smaller

bulb on another tube, and applies its end, while yet soft, to the soft extremity of the leg; the small bulb is then detached from its tube, and after having been softened by exposure to a hole in the furnace, is expanded by the pro

cello into a flat foot (fig. 7). A punto tipped with melted glass is next ap

Fig. 7.

plied to the centre of the foot, the blow-pipe is detached, and the body of the glass is fashioned to the required shape in the manner described above for the bell-jar. An endless variety of forms may be obtained by the dexterous combination and modification of the manipulations above alluded to.

Imitations of cut-glass vessels are made by blowing the soft glass into a polished metallic mould, the form of which it acquires with as much faithfulness as wax.

The annealing arch is a rectangular arched chamber of from thirty to forty feet in length, three feet in height at the centre, and about four feet in width. One end of the chamber is moderately heated by a small stove, the smoke and hot air from which pass along the gallery to about two-thirds of the length of the latter, where they are discharged by a chimney. The vessels to be annealed are introduced into the arch at the heated end, being disposed on shallow iron trays, called "leer-pans," which are usually placed in two rows on the floor of the chamber; and as one of the trays is removed at the cool end, another empty one to receive more hot glasses is introduced at the heated end.

The time required for properly annealing small and thin vessels of flint-glass is from twenty to twenty-four hours. As thick vessels require a much longer time, and also a higher temperature at the heated end, than thin vessels, it is usual to have two or three of these annealing galleries attached to the same working furnace, so that the process may be conducted, if necessary, in a different manner with different articles, at the same time without interruption.

The variety of glass known by the name of Strass, which is used as a general colourless basis for factitious gems, on account of its remarkable lustre, belongs to the same class of vitreous bodies as flintglass. The chief difference between the composition of strass and flint-glass consists in the former containing the largest proportion of oxide of lead. Some manufacturers also introduce a small proportion of borax. With the basis alone, by being worked on the lapidary's wheel, excellent imitations of colourless diamonds may be obtained; and by uniting it by fusion with various metallic oxides, a great variety of precious stones are counterfeited.

Great regard should be paid to the state of purity of the materials from which strass is prepared. The presence of oxide of tin in the litharge or red lead, and of oxide of iron in the sand, should be particularly avoided, as the former would communicate an opacity, and the latter a yellowish or greenish colour, to the glass. To ensure the absence of oxide of iron in the sand, that material should be calcined and

So called from the name of its German inventor.