PRINTING PRESSES. 



Printing to effect that rapid increase of power, near the end of 

 1'reises. t he y u \] t -which has been already mentioned as the 

 L- v O g reat desideratum in the construction of .this part of 

 the printing press. 



To determine the actual gain of power at the begin- 

 ning and at the end of the pull, measurements have been 

 taken from an individual press, of the lines necessary 

 for the computation. When the bar was thrown back, 

 the angle ACD (of the triangle ADC, formed by join- 

 ing the three centres of motion with straight lines) was 

 found to be = 11 3 52', CD A = T 12', and the dis- 

 tance of the centre of motion of the two adjacent ends 

 of the main levers from the straight line joining their 

 outer extremities = 2^ inches. The length of AC was 

 3i, and the distance from A to the part of the handle 

 where the hand was generally applied was 24 inches. 

 Hence, as will appear from the theorems given above, 

 the gain of power will be found by compounding the 

 following ratios : 24 to 3 ; cos. 70 12' to sin. 113 52' ; 

 15 to 2 x 2^; and H< to 15 ; which gives a total of 

 20 to 1. 



At the end of the pull the angle ACD = 172, the 

 angle CDA = 13', and the distance of the vertical 

 levers from a straight line, according to the specifica- 

 tion of the inventor, which was found nearly exact, 

 rr half an inch. Hence the gain of power will be 

 found by compounding the following ratios : 24 to 3| ; 

 cos. 1 3' to sin. 172 s ; 15 to 2 X ^; and 14 to 15; 

 which gives a result of 76'3 to 1. It thus appears that 

 the power gained is about thirty-eight times greater at 

 the end than at the beginning of the pull." 



Hope's Printing Press. 



Hope's One of the latest printing presses is that invented 



printing anc j constructed by Mr. Hope of Jedburgh, who has 

 secured it by a patent. This press, which is repre- 



Fig. 9. sented in Fig. Q, is an improvement on the Stan- 

 hope press; and the patent is taken out merely 

 for a new combination of levers. A plan of that 



Fig. 10. p ar t of the press is shown in Fig. 10, where a, a 

 are the iron standards of the press, and b the plattin, 

 with the form of types under it. The handle d of 

 the press is attached to the short arm, or lever e, turn- 

 ing on a pivot in the iron pillar a. The connecting 

 rodyis fixed to e by a joint, and in the usual construc- 

 tion of the Stanhope press, it is connected to another 

 short arm fixed to the metallic screw or bolt in the 

 joint of the press. In the present new construction, 

 toowever, the rodjfis connected by a joint to one arm 

 of the forked lever g, which moves upon a cylindrical 

 fulcrum on the pillar , while the other end is joined 

 by a pivot to the posterior rod //, jointed to a short arm 

 i, extending from the bolt of the press. Mr. Hope there- 

 fore gains additional power, by using the additional 

 connecting rod h and the bent lever g. 



When the press is at rest, the combination of levers 

 has the position shown in the figure ; but -when it is 

 in action, the path described by the different parts is 

 shown by the dotted line. 



In place of the male and female screws by which the 

 plattin generally rises and falls, he substitutes two in- 

 clined planes; but these do not form a part of his pa- 

 tent. 



This press has been used in several printing offices 

 both in England and Scotland, and it is admitted to 

 unite the advantages of cheapness with great power and 

 accuracy. 



Printing 

 Tresses. 



Several other presses have been contrived. In 

 Brown's press, for which a patent was taken in 1807, 

 the screw is moved by a bevelled wheel and pinion, 

 and the types are inked by two elastic rollers. Brookes's 

 press consists in the application of the compound le- 

 vers of the Stanhope press to the commtn press. 



PRINTING PRESS, COPPERPLATE. The inven- Copper- 

 tion of the copperplate printing press seems to have P |ate print- 

 been made about the same period as the type printing in S P ress - 

 press. In the absence of authentic record, tradition 

 has ascribed the discovery to a silver-smith, who in 

 order to save labour, and insure the accurate and rapid 

 multiplication of engraved patterns upon his works, 

 was in the habit of inking in the pattern, and taking 

 off impressions with a burnisher from the figure first 

 executed. This is so simple, and generally so well 

 understood a process, that we need not waste time in 

 describing it. 



The success attending this discovery, immediately 

 suggested that the same results would be obtained in 

 a more perfect manner, by a proper application of the 

 pressure of a roller to the whole surface of the plate at 

 once, instead of the labour of passing the burnisher 

 in the hand gradually over each individual spot of en- 

 graving. The first invented presses appear to have 

 been constructed with considerable accuracy and power 

 from the excellence of the impressions of the ancient 

 works which have reached us, but which it would be 

 out of place to enumerate here. 



In the present age of improvement, and novelty, 

 many alterations, and certainly great amendments 

 have been made, both upon the construction of the 

 press for the higher branches of printing, and also 

 upon that adapted to more ordinary purposes. Among 

 the most prominent of these improvements is the ap- 

 plication of the wheel and pinion, instead of the lever 

 or cross for driving the press, and the substitution of 

 cast iron in place of wooden rollers. Other plans 

 have been suggested for the purpose of increasing the 

 rapidity of multiplying the impressions of common- 

 place works, the most ingenious of which is the inven- 

 tion of the celebrated Mr. Perkins, and of which a 

 complete account will be found in the London Jour- 

 nal of the Arts, No. III. Plate VIII. Figs. 3 and 4. 

 We shall describe these presses after we have detailed 

 the construction of the more simple machinery ; but 

 before proceeding, it may not be out of place to re- 

 mark, that the principal requisites of a good copper- 

 plate press are perfect truth in the manufacture of the 

 rollers and plank interposed between them, and the 

 judicious application of such a working power as 

 shall cause the least bodily fatigue to the printer. 

 If the workman has to apply too much of his strength 

 to drive the machinery, his hand will be made to 

 shake in consequence of the exertion, and thus he 

 will be rendered incapable of cleaning off the ink from 

 the plate, with that delicacy of touch which is indis- 

 pensably requisite in finer works. The printers of 

 calico goods, aware of the importance of this con- 

 sideration, have skilfully applied the power of the 

 steam engine for this purpose ; and we have been in- 

 formed that the presses in the bank of Ireland for 

 printing their notes, are also driven by the same 

 means. 



Fig. 11, Plate CCCCLXVIII. represents the most Pi, ATE 

 simple copperplate press, which, with the exception of CCCCLXVIII, 

 the spindles of the two rollers, may be entirely con- Fi - J1 - 

 structed of wood. A is the upper roller, B the under 



