more subject to decomposition than uncolored glass. The iridization seen on ancient colored glass was not intentional in the fabrication, but due to chemical changes of the surface; long exposure and atmospheric influences causing a separation of the constituent parts and producing the minute flakes of glass which reflect the light at various angles and give out prismatic hues.

be

Similar prismatic effects can now produced by the fumes of certain chemicals diffused over the surface of a glass vessel during the "blowing" process, and made permanent by reheating at the furnace immediately after the fuming has taken place. As with the ancient iridescent glass, dark grounds -- especially greens and blues-throw out the prismatic colors best.

Whenever substances containing silica and alkali are subjected to intense heat, there is always the possibility of glass formation; as for instance, reeds or straw burnt in very large masses. Metallurgical operations, such as the smelting of ores, have produced glass. Glassmaking history often refers to remelting glass. Lumps of glass sent from Spain to the Roman glass-workers were remelted when coloring materials had been added. Efforts to produce a superior glass for rich cutting have been successful when the whole first melting of the flint "batch" has been taken from the melting pot in an iron ladle and plunged into a cauldron of water, the effect being to break up the glass into small particles, in appearance like cracked ice. It was then refilled, corrected in color if necessary and remelted, producing a glass as nearly perfect as possible for cutting purposes and free from the striæ present at the first melting.

Glass at a high temperature is fluid and solidifies as the temperature is reduced. When regulated to a semi-fluid state it becomes tractable and its ductility admits of its being manipulated in a variety of ways; blown hollow through an iron blow-pipe, cast in a mold, pressed in a machine or with hand pincers, drawn out into lengths- either solid or hollow, rolled into plates, whirled into discs or sheared as cloth is cut with scissors. The peculiar tenacity of the substance enables any of these processes to be performed, but only by a practised hand, and as the metal rapidly cools, the several operations must be rapidly performed. The molten glass commences to harden immediately it is drawn from the pot in the furnace and quickly becomes incapable of expansion by air or manipulation by tool, but it can be softened to the working condition again by a plunge into any sufficiently heated enclosure, usually the mouth of the melting pot.

A moderate heat is required for the welding of glass, and handles or applied ornamentation can be made quite secure if the parts of union are without sulphur or smoke from the furnace, both of which elements prevent perfect cohesion of the parts. It is necessary to reheat quickly after the union is made. A cold metal coming in contact with a glass form upon the blowing iron when just cooled to hardness will initiate a fracture at the chilled part which will extend through the whole of its thickness when given a light blow, and separate the form from the

iron rod or tube- upon which it has been fashioned. These principles of welding and fracturing, both instantaneous in operation, are important factors possessed by no other material. JOHN A. SERVICE.

GLASS, Cut or Incised. See GLASS, ORNAMENTATION OF; GLASS, VARIETIES OF.

GLASS, Ornamentation of. In the preface to one of his textbooks upon the application of art, Lewis F. Day says: "It is only in theory that ornament can be independently discussed. Practically it exists only relatively to its application." "The necessity of adapting design to its position and use is as obvious as it is absolute." These axioms are especially true in regard to the ornamentation of glass, as well from the nature of the material itself as from the variety in form to which ornament is at once a necessity and a complement. The earliest known manner and process employed in the ornamentation of glass was in all probability suggested by the "rugged excrescences» which disfigured the first "metalline form” described in Dr. Johnson's eulogy. By manipulating these excrescences and giving direction to the flowing metal, the first effort at ornamentation was accomplished. The same motive is carried out in every epoch of glass-making history from the earliest Egyptian times right into our own day. The principle is that of patterning or initiating a foundation for patterning by the manipulation of glass in its molten state, either by scoriation of the mass or by welding upon the surface of a partly fashioned form during the process of fabrication at the furnace. From the development of this primitive motive many of the most interesting and most beautiful decorative features known to the glass-making industry have been evolved. It is the base of the whole range of the reticulated classes of ornamentation which have characterized the efforts of glassworkers in many periods and in most countries. Antique examples in our museums show that ancient craftsmen in the East practised extensively this appliqué mode of ornamenting glass. The Greeks and Romans adapted it in various ways. It was a feature in Persian and Byzantine glass-making. Venice employed it in creations which have influenced ornamental glass production wherever the art has been cultivated during the last five centuries. Spain commenced its ornamental glass production along the same lines and the earliest known drinking vessels of glass used in Britain supposedly of Roman origin - possessed the same constructive features. It needs no great stretch of the imagination to trace back such contributions to usefulness in glasswares as handles, stems and feet to this parent stock. The whole range of decorative motives resulting from the manipulation of lumps, strips and threads of glass welded upon the surface of a blown form, belong to this class. There are few records of the manipulating processes employed by the ancient glass-workers in turning these welded parts into ornament, but to one conversant with the material the difficulties are oftentimes not so great as they would appear to be. The ornamental treatment to follow the applique form is largely a matter of surmise, but the evidences are in favor of some form of cutting

upon a wheel and the gem lapidist seems entitled to the credit of introducing it. Most of the early practised means of abrading glass ornamentally came within the term "cutting," though they embraced grinding, scraping, rubbing and scratching.

Ancient examples of transparent glass in the British Museum show unmistakable signs of having been "cut" by means identical with those in use in our own time and it would appear to be unnecessary to look beyond them in an attempt to fix the origin of cut glass. Illustrations and descriptions of these examples appear in 'The History of Art in Chaldea and Assyria' by Georges Perrot and Charles Chipiez (Vol. II, pp. 306-307). Layard discovered them at Nineveh. The first named may have been used for some precious unguent. The description says: "It has been blown solid and then the inside cut out by means of an instrument which has left easily visible traces of its passage; this instrument was no doubt mounted on a lathe."

outline.

after "turning" it into shape - taking up the first glass object ready to his hand and by a chance abrasion discovering a means of ornamentation the very antipodes of the hitherto one and only "appliqué" method, i.e., cut glass. The "cut" upon this antique is known as the "olive" and is formed upon a convex-faced wheel such as may be used to "concave" a lens the size of the wheel and the curve of the surface worked upon determining its By encircling a tube form with a row of "olives" joined together, then repeating above and below in alternate spaces the first row of cuts automatically assume the "lozenge» form. The irregularity of the placing of the cuts is suggestive of the eventual lozenge pattern occurring from the accidental joining of a number of haphazard cuts, thus the entirely surrounded "olive" would become polygonal, while the partially free would have the "scalelike" appearance observable. Drawings B and C show these effects on tubes of same shape with "cuts" arranged in regular order. (For

Drawing A (top). Drawing B

Without relying upon the "blown solid" argument the suggestion of a cutting instrument which left visible traces of its passage comes very near to the glass-cutting operations of subsequent times and incidentally is both an early suggestion of the principle of stoppering a glass vessel to preserve its precious contents and the advantages of transparent glass over other substances for such purposes of preservation.

The second example comes nearer still to cut glass as we know it. It is described as "a glass cylinder or tube of unknown use; it is covered with a decoration made of lozenges with a concave surface." (See drawing A). The theory that it represents the beginning of glass-cutting gets some support from the class of cut distributed over its surface. In assuming its period to be about 700 B.C., it is not difficult to imagine the Assyrian lapidist who ground into shape the rock crystal lens discovered at same time and place (see Layard's 'Discoveries, page 197), when about to make the always necessary test of his stone wheel

(center). Drawing C (bottom).

application of this motif see The Art Journal 'Report on International Exhibition,' London 1851, pp. 32, 175). Most facetted patternings upon cut glass are produced automatically from the crossing and recrossing of the lines of ornamentation. The remark "of unknown use" for this antique object has its significance. Possibly it had no definite use; the form being the usual experimental one of the glass-blower when testing the clearness of his "metal" and is the preliminary of many blown shapes, frequently never passing beyond this limit owing to various kinds of defect. The entire absence of any similar antique supports this theory.

The bas-relief ornamental glass (better known perhaps as cameo) of ancient Greece and Rome, was a form of "cutting," the ornamentation being effected in part by the lapidary's wheel and it is probable the essential to finished cut glass-polishing. was in those times, as now, accomplished partly on the wheel.

The most famous examples of bas-relief ornamented glass known- the Portland vase

has a highly polished surface and one of the arguments used to support a theory of Greek origin for this classic gem is based upon the known proficiency of the ancient Greek sculptor in the toreutic art.

Any incisory form of ornamenting glassby diamond or hard metal point or by lapidary's wheel was usually described by early historians as "cut," but in the 13th century there are Constantinople records of "glass cups and shallow basins cut with the wheel." That this was the true type of cutting may be inferred from the description given - "one cup has the surface so cut away that small cones are left standing up (the diamond cutting of to-day) and another has circles formed in same manner." The writings of Chardin (mid-16th century) record Persian glass bottles "cut diamondwise." There is a Bohemian claim to the invention of cut glass early in the 17th century, but as the art was not unknown in ancient Assyrian times and there are evidences of its practice in the early medieval, this claim may have been based upon the discovery of some advanced production of the cutter's wheel; possibly the one which in later times proved such a boon to the glass industry in several of its departments, not only in Bohemia but in other countries, especially England about the middle of last century. This feature was developed from the substitution of "intaglio" for "relief" ornamentation upon cased glass of the kind formerly used so extensively by Roman glass-workers. Any colored transparent glass formed the base and an outer coating of opaque white served as a ground for the ornamentation which was cut through the casing into the substance beneath; the contrasting colors clearly defining the lines of the pattern.

Cut-glass patternings are produced by first grinding away the main lines of the design upon an iron wheel, with fine sand and water, streamed between the wheel and the glass, as the cutting medium. The second process is performed upon stone wheels, of shape and size corresponding with the iron wheels and kept wet by contact with a moistened sponge. This operation gives definite form and a smooth surface to the cut. The polishing is effected in various ways by wheels of wood and cork; by wheel brushes and by an acid bath. The wheel polishing mediums are finely ground pumice and rotton-stone mixed with water, for first process; and afterward a putty-powder made from lead and tin, also mixed with water. The acid bath is hydrofluoric. The iron wheels rotate toward the operator, other wheels the

reverse way.

As some of the descriptions of early "cut" glass most assuredly point to finely engraved intaglio ornamentation, with figure subjects a frequent motive, the glass-engraver's art must be accredited with quite ancient origin. An 8th century example is known but some of its ornamentation is so filmy that it may have been effected by a sharp pointed instrument instead of the metal wheel. In 15th century history engraving is mentioned in connection with German, Dutch, Venetian and French glass. By end of the century it had advanced considerably and the craftsman of that period was styled "lapidary and glass-cutter."

For some considerable time after the 15th century the best work appears to have been done in Germany and Austria - the Bohemians being especially expert craftsmen — though the art was practised in several other European countries. The Spanish town of La Granja was famed for its engraved glass and as decorated mirror making was also a feature of production there the engraved mirrors (of the type shown in illustration) occasionally met with in southern Europe, may have originated there. Excellent engraving was done in France, Holland and England throughout the 18th and 19th centuries. Cut glass of the later Georgian periods produced in England, Ireland and Scotland received aid from association with the sister art of engraving and by this co-operation ornamental motives were carried to completion that could only have been partially effected by either one of the processes. The broad features of ornamentation were usually "cut"; the more intricate parts "engraved."

Since about 1850, the art of glass engraving in its highest development has been extensively cultivated in the English manufactories. The coming of the international exhibition was the incentive. Artists were encouraged to step outside the commercial production and create a fine-art standard. The Elgin marbles claret jug (see illustration) was produced at Stourbridge for the Paris Exhibition of 1878, has been "round the world" for exhibition purposes and is now in a private collection in London. Engraving of this type is performed upon small copper wheels riveted upon the end of an iron spindle set in the mandril of a lathe and rotated by a foot treadle. The cutting medium is fine emery powder mixed with a thin oil. The engraving is done under the wheel and as the cutting medium obscures the actual contact of wheel and glass, the direction and duration of each cut is a matter of judgment. The glasscutter works over the wheel and the progress of the "cut" can be observed through the glass. Polishing of the dulled surface left by the emery can be effected upon same lathe and form of tool with wheels of lead; with finely powdered pumice, mixed with water, as the brightening medium. The "lead-wheel" process of polishing engraved glass was the customary one until quite recent years. The subject on the engraved mirror illustrated shows its application. The parts shown black, upon the white ground, are the lead polished portions of the engraving. When adapting the engraver's art to the production of imitations of carved rock crystal in the last seventies- lead polishing had to be abandoned as too slow a process. The rock crystal effects in glass gave a new lease of life to the engraver's art and opened new fields of operation for the most highly skilled of its craftsmen and its adoption as a new ornamental feature may be set down as the most important development, artistically, the table-glass industry has known in recent times. A true rock crystal effect in glass can only be obtained by complete restoration of the dull engraved ornamentation to brightness. At first, the polishing was done upon wheel brushes, but this was still too slow a process to meet the great demand which was eventually satisfied by the more rapid and far more effective -acid bath process. The Elgin marbles sub