As it is impossible but that there must be some mistake in the work, either through the oversight of the compositor, or by the casual transposition of letters in the cases, a sheet is printed off, which is called a proof, and given to the corrector, who, after reading it over, and rectifying it by the copy, making the alterations in the margin, returns it to the compositor to be corrected. The compositor then unlocking the form upon the,correcting stone by loosening the quoins or wedges, rectifies the mistakes by picking out the wrong letters with a slender sharp-pointed steel bodkin, and putting others into their places. After this, another proof is made, and corrected as before; and lastly, there is another proof called a revise, which is taken from the form when finally placed on the press, in order to ascertain whether all the mistakes marked in the last proof have been corrected.
The promotes business is to work of the forms thus prepared and corrected by the compositor; in doing which, there are foUr things required—paper, ink or colouring matter, balls or rollers, and a To prepare the paper for use, it is to be press. Toby dipping several sheets together in water; these are afterwards laid in a heap over each other; and to make them take the water equally, they are pressed close down with a weight at the top.
The ink is made of oil and lamp-black ; for the manner of preparing which, see I xx.
The balls, by which the ink was formerly applied on the forms, were • kind of wooden funnels with handles, the cavities of which were •lied with wool or hair, as was also a piece of leather or pelt nailed over the cavity, and made extremely soft by soaking in urine, and being well rubbed. One of these the pressman took in each hand, and applying one of them to the ink-block, daubed, and worked them together, to distribute the ink equally, and then blacked the form, which was placed on the press, by beating with balls upon the face of the letter. A considerable improvement on this plan has been effected by means of rollers, which are now generally in use. These consist of a cylinder made of a combination of treacle and glue, which runs on an iron rod, affixed to which are two handles. Instead of beating, as in the former case, the cylinder is rolled over the face of the form, by which the ink is applied in a much more even manner, and with a considerable decrease of labour.
The earliest printing presses were the common large wooden screw presses, employed at the present day for compressing paper, cloth, &c. Of course this mode of taking impressions must have been very slow and laborious; and the pressure being applied between the two solid inelastic surfiices, a considerable degree of care must have been exercised to prevent injury to the letters or type of the form. Such presses were, however, used for about 300 years, without any one attempting to improve them. A short time previous to the year 1770 it appears that William Jansen Blaew, a mathematical instrument maker, of Amsterdam, recommended the introduction of a spring, both over the head and under the bed of the press, which, upon trial, proved very satisfactory ; he took upon himself an:alteration of the working screw, giving it more threads, which is, in effect, a quicker motion ; and this, combined with the action of the springs, rendered the impression "sharper," without "hardness." Blaew's presses were
found to be so great an improvement upon their precursors, that Luckcombe, in his History of Priding, published in 1770, says, " There are two sorts of pm**. in use, the old and the new fashioned; the old sort, till of late years, were the only:presses used in England." Now the " new-fashioned " press of Blaew, thottgb it has become very old-fashioned to modern Orinters, is too respectable a machine, in our eyes, to be wholly omitted in these pages • and as it differs not in any considerable degree from the wooden-framed presses shill in use by many of our printers, we shall here annex a description which will sufficiently apply to them both. It consists of two upright beams, called cheeks, about six feet long, tenoned into a cap above, and, at their lower ends, into a stout square frame, on which it stands. The head of the press is sustained by two iron bolts, that pass through the cap. A screwed nut is fixed in the head, through which the screw works when operated upon by the lever ; the lower extre mity of this screw is called the spindle, which is a cylindrical piece of steel working in a metallic cup of oil, fixed to an iron plate let into the top of a broad, solid, and thick piece of mahogany, whose surface is brought to a true and smooth plane, and is called the platten. This platten, by pulling the lever, is made to descend and press upon a blanket, which covers the paper laid upon the form of types, and thereby produces an impression. The form is laid upon a broad flat stone, or thick marble slab, which is let into a wooden frame called a coffin ; this coffin is fixed upon a carriage, which is made to run upon a hori zontal railway under the platten for an impression, and out clear of the same, to take off' the printed sheet, and put a blank one in its place. This backward and forward motion of the carriage and form is produced by a strap and pulleys, turned by a winch handle. The paper is adjusted and held down by a folding frame, called the tympan and frisket, which again fold down over the fresh inked type, in a very exact manner, before the form is run in under the platten to receive an impression. By presses of this kind, about 250 impressions are run off in an hour ; in light work it is extended to 300 in an hour ; and when presses of this kind were used for printing newspapers, the printers managed by extraordinary efforts and relays of men, to work as many as 500 in the hour.