a c b is an angular lever, whose longer arm a c is in the form of a winch, to which the workman applies his power ; while the shorter arm c b acts upon the extremity of the connecting rod d, by which its efficacy is trans mitted to the point e of the lever e f, whose fulcrum is at g; this lever is connected by the rod It to the extremities of the levers m, whose fulcra are m m. The rods nn are connected with the levers k 1 m at 11, while their upper ends act upon the support of the platten by means of a species of hooks. Now if the lever or winch a e be turned in the direction of the dotted line a o, the shorter arm cb will push the rod d in the direction 6 e; consequently the point e of the lever e f g will move in the direction of the dotted line ep; and as the point f will describe a similar arch, the rod k will depress the ends k of the levers kin; therefore the rods n n will be drawn down, bringing with them the platten. The same regulation with regard to the angular positions of the levers is observed in this beautifill arrangement as in the Stanhope, so that their greatest efficacy is exerted at the moment of impact.
Mr. Medhurst's press, except in the mechanist by which the power is com municated to the platten, resembles those in general use ; but in that respect it forms a very remarkable exception ; no screw b used : but the spindle to which the platten is made fast is swelled out at its upper end into a broad stout collar, as shown at a in the following cut, into which the lever or handle 6 of the press is inserted. At equal distances apart on the upper side of this circular collar are turned out of the solid two steps or cups, which receive the ends of two inclined bolts c c, which bolts are supported at their upper ends by the points of two screw-bolts dd, that pass through the head e, and enter sockets made in the heads of e e. When the platten is up, the rods e c lean in the inclined position, as shown; but when the spindle as turned a quarter of a revo lution, the bolts c c take a vertical position, and as the head e it immovable, the collar a on the spindle is forced down, and with it the platten to which it is attached.
Prior to the introduction of printing machines, the press department was one of great labour, whenever extraordinary expedition was required. It was par ticularly the case with newspapers, of which, with the utmost exertions, scarcely ever more than 750 copies could be obtained in an hour: the consequence was, that in newspaper offices where the circulation was extensive, it was found necessary, in order to get the paper published in time, to compose two or more copies; so that, by going to preu at the same time, die demands of the public might be complied with, thus occasioning an enormous increase of expenditure both in the compositors' and press department. In a newspaper circulating
7 or 8000 copies, this expense amounted annually to at least 20001., all of which has been saved by the introduction of machines.
In the 3d vol. of the Quarterly Journal of Science (new series) is inserted a communication " on the recent improvements in the art of printing," by Mr. Cowper, a gentleman of extensive information upon every thing relating to the subject, who has invented many important improvements in the mechanism and process of the art, both individually, and in conjunction with his partner, Mr. Applegath, and who is therefore eminently qualified to Five a correct statement of the faets, which we shall subjoin, slightly abbreviated from the original. The little diagrams that are inserted in the body of the text serve to explain, in a very clear and concise manner, the leading principle or arrange ments of the successive inventions described, respecting which it is also neces sary to observe, that— It was in the year 1790 that Mr. William Nicholson took out a patent for certain improvements in printing; and, on reading his specification, every one must be struck with the extent of his ideas on the subject : to him belongs, beyond doubt, the honour of the first suggestion of printing by means of cylinders ; the following are his own words, divested of legal redundancies :— " In the first place, I not only avail myself of the usual methods of making type, but I do likewise make and arrange them in a new way, viz. by ren dering the tail of the letter gradually smaller; such letter (he says) may be imposed on a cylindrical surface ; the disposition of types, !plates, and blocks, upon a cylinder, are parts of my invention.
" In the second place, I apply the ink upon the surface of the types, plates, &c. by causing the surface of a cylinder, smeared with colouring matter, to roll over, or successively apply itself to the surface of the types, &c., or else I cause the types to apply themselves to the cylinder. It is absolutely neces sary that the colouring matter be evenly distributed over this cylinder, and for this purpose I apply two, three, or more smaller cylinders, called distributing rollers, longitudinally against the colouring cylinders, so that they ma7 be turned by the motion of the latter ; if this colouring matter be very thin, I apply an even blunt edge of metal or wood against the cylinder.