On Printing Presses and their Theory. 313 



er that there is a gain of power, which gradually increases 

 as the two halves approach a straight line, and becomes im- 

 mensely great at the moment this position is attained. The 

 thrust of two such arms is precisely the same, and varies ac- 

 cording to the same law for different angles, as the -pull in 

 the simplest case of the funicular polygon ; that is, when a 

 rope is tended by a certain force and is drawn aside from 

 a rectilineal position by pulling at the middle. 



This principle is introduced in different forms into the 

 Ruthven, Stanhope, and Columbian presses. In that in- 

 vented by Earl Stanhope it is employed to give a diminish- 

 ing velocity to the screw : in the Columbian press of Mr. 

 Clymer, it is employed to give a diminishing velocity to a 

 large lever of the second kind, which is substititted for the 

 screw. These two presses, especially the latter, from their 

 durability, the neatness and uniformity of the impression 

 they produce, and the diminution of labour they occasion 

 to the pressman, have been justly held in high estimation. 

 To the excellence of the Columbian press, honorable testi- 

 monies have been borne in foreign countries : among others 

 has been a present of six thousand rubles to the inventor 

 from the Emperor of Russia. 



But of all the presses which act on the principle of com- 

 pound leverage, the one recently invented by Mr. Wells, 

 of Hartford in this State, appears to possess the highest re- 

 commendations. It has now been in operation in various 

 parts of the country more than two years, — a period suffi- 

 ciently long to furnish an experimental test of its excel- 

 lence ; and it seems due no less to the interests of the me- 

 chanical arts in this country than to the ingenious and wor? 

 thy inventor, that a more particular account of it than has 

 hitherto appeared should be given to the public. 



A perspective view of this elegant piece of mechanism is 

 given, plate II, fig. 1. The frame is of iron, cast (with the 

 exception of the feet) in a single piece ; and is of such form 

 and dimensions as to be incapable of springing, while the 

 press is in operation. The platen (4) is of cast iron, and is 

 of the dimensions of an entire form. The circular projec- 

 tion in the middle, with six radiating pieces, gives it an am- 

 ple degree of firmness. The platen is immediately acted on 

 by bringing nearly into a straight line the two main levers 

 (6) and (17). These levers, in presses of the medium size. 



Vol. in No, 2. 40 



