THE NEW-YORK EXHIBITION ILLUSTRATED.

theory of heat which treats it as an elastic fluid, is striking and eminently suggest-ive, though too recondite to he more than mentioned here. There is then a vastfield of research, full of interest and promise, for whose exploration this ther-mometer is, we helieve, the most reliable instrument, and we trust it will there-fore be put into increasingly active requisition.

TYPE FOUNDING.

THE early printers in Germany made their letters in Gothic and semi-Gothic"*■ forms; and Caxton, in England, and Antoine Yerard, in France, printed theirWorks with a style of letter imitating the handwriting of that period. In Italy,under the influence of the beautiful manuscripts, more common there than else-where, and of the excellent taste of the early printers, the form of the letters wascompletely changed into the style which we use at the present day, under thename of Roman letters. In 1462, Louis XI., of France, sent Nicholas Jenson, anengraver in his service, to Mayence to learn the new art of printing. But Jenson,for political reasons, established himself in Venice, and engraved there the beauti-ful Roman characters, which Garamond afterwards took as models in engravingthe types employed by the Elzevirs in their celebrated books. The Roman charac-ters were also adopted by the Aldi and the Stephani, whose beautiful and finishedWorks it is the glory of modern printers to imitate and rival. But little improve-ment has been made in the art of casting types since its invention, which goeshack to the origin of printing itself. The types made by Baskerville and by Didot,m'e not more elegant and perfectly finished than the earlier masterpieces of thear t which we have mentioned. The innumerable changes which have been intro-duced mto the shapes and relative proportions of letters by the caprice of modernengravers, are retrograde changes, the fashion for a while, and then forgotten. The°ld letters of Garamond and Jenson have been again employed by Pickering andother eminent English publishers, and will probably always maintain their placeWith printers of taste.

In the United States, types were first cast in 1735 by Christopher Sower, atGermantown. Unsuccessful attempts were made in 1768 to establish type-foundries,°ue in Boston, and another in Connecticut; but not long after the close of the War°f Independence, the first regular type-foundry was set up in Philadelphia byHaine, who came there from Edinburgh. In 1790, Messrs. Binney & Ronaldsonnlso commenced the business in Philadelphia, and met with great success fromfhe gi'owing number of newspaper and other job offices, which, in ten years, in-creased the amount of printing threefold, and caused a corresponding extension offhe business of type-founding. These gentlemen are credited with the first im-provement made in the art since its invention. It is a type-mould, which was in- \froduced into Europe at the commencement of this century, and is known therens the American Mould. By this mould 6000 types are cast as easily as 4000 by the°hl process. The first extensive foundry in New-York was established in 1811,hy Mr. White. He had before been a type-founder in Hartford, where he hadinvented and used a method of casting several letters together, but this deviceWas dropped after his removal to New-York. Another type-foundry was erected1813 by Messrs. Bruce. The business has since been extended to keep paceWith the increased number of newspapers and books published here, and each offhe principal cities of the Northern and Western States now has one or moretype-foundries. These give employment to about 800 persons, and produce dailybetween 4000 and 5000 pounds of type. They furnish nearly all the types used onthis continent. Some of the finer book-work is still done, however, with Englishtypes, and the Oriental founts, and the beautiful Porsonian Greek type, employedat Mr. Trow’s University Press in this city, are also imported.

The first and most important step in type-founding is to prepare the punches.They are pieces of soft steel, upon each of which the engraver cuts a single letterW] th all possible accuracy, and they are then carefully tempered. The face of thePnnch resembles the finished type. Its impression, made in soft copper, is calleda matrix; it is the mould which forms the face of the type. The mould of the®hank is made of two pieces of steel, which fit accurately to each other and thematrix, and are inclosed in wood for convenience of handling. The type metal18 poured into a funnel-shaped orifice at the top, and by a peculiar movement of^h® caster’s arm, is thrown into the cavities of the matrix. When the metal iss ®t, the founder detaches the matrix from the face of the type, and the mould isthen opened and the type removed. The overplus of metal which filled the fun-nel is next broken oflf, and the sides of the types are rubbed smooth, after which^hey are secured in frames, and have their ends cut smooth, and the lower one alsojP*°und. The process of ftearding, which consists in bevelling the angle of thebo<1 y below the letters, is performed at the same time. Types of the same founta ^e distinguished by one or more nicks upon the lower edge or end, which enablesb 6 compositor to set them correctly without looking at each. The compositionof type metal is various. Lead forms about 75 per cent, of the alloy; it is united

most commonly with antimony, but sometimes with copper, brass, tin, or bismuth.Within a few years, types have also been made by powerful steel punches fromplates of cold copper; but we have not learned whether they have come into use.

The first successful machine for casting type was invented twenty-five yearsago, by Mr. William M. Johnson. It did not come into general use, probably be-cause the types manufactured by it were not as solid and durable as those madein hand-moulds. The latter continued to furnish the ordinary means of type-casting until six or eight years since, when the Type-Casting Machine, of whichwe give an engraving, was invented by David Bruce jr., of New-York. Its meritshave been thoroughly tested by L. Johnson & Co., of Philadelphia, who exhibitthe machine, and cast type with it in the Crystal Palace. These gentlemen haveapplied it in their extensive establishment to the manufacture of almost everyvariety of type, and have attained a degree of finish and accuracy entirely satis-factory. The peculiar merit of Bruce’s Machine is, that it produces solid and sub-stantial types with great rapidity—the limit being in the time required for themetal to solidify after entering the mould. The force with which the liquid metalis injected into the mould is so great, that the proportion of the defective lettersis much smaller than in hand-casting. The fine lines of the matrix are broughtout sharp and unbroken.

The space occupied by the machine is about 14 by 20 inches; including thewooden frame on which it rests, it is three feet high. A pot filled with type-metaloccupies the back part, and a small furnace, fed with anthracite coal, is placed be-neath it, or a gas-burner powerful enough to maintain the fluidity of the metal. Acylindrical tube or pump, stands vertically under the metal, and has a spout project-ing from the front side of the pot. A piston rod, set in motion by a revolving crank,moves up and down in the cylinder, and at every revolution injects a small quantityof the metal into the mould, which, at the proper moment, comes closely up to thespout to receive it. After the metal has been received and hardened, which is donealmost instantly, the mould recedes a few inches, its upper half rises, and the typeis thrown out into a gutter leading to the receiving box. The type is then ready tobe finished as we have already described. The power required for the various move-ments, is communicated by cams arranged along an axle, whose crank is turnedby the right hand of the caster.

All, or nearly all, the types produced in American foundries are cast by ma-

chines ; the only exceptions that we know of being large, ornamental type. Ma-chines have been sent from the United States to Europe, and others have been in-vented there, but they have not been much used except in Germany. They arewell known to type-founders in England, but have never been employed by them,