On Printing Presses and their Theory. 311 



MECHANICS AND ARTS, CHEMISTRY AND PHYSICS, 



Art. IX.— On some recent improvements in the construction 

 of the Printing Press ; with a particular notice of that 

 lately invented hy Mr. John I. tVells, of Hartford, Ct. 

 by A. M. Fisher, Professor of Mathematics and JYatu- 

 ral Philosophy in Yale College. 



The principal defect in printing presses of the ordinary 

 construction, so far as the mechanism employed to procure 

 a gain of power is concerned, consists in the want of adap- 

 tation of this power to the variable resistance which is to be 

 overcome. The elastic substances interposed between the 

 form of types and the platen, present at first a compara- 

 tively trifling resistance ; but it gradually increases as the 

 platen descends, and must finally be made immensely 

 great, in order to attach the ink with sufficient firmness to 

 the paper. But to overcome this resistance the mechanical 

 advantage furnished by the screw is perfectly uniform. To 

 make up for the want of an increasing advantage in the me- 

 chanism, the pressman is obliged to place his body in such 

 an attitude that his weight shall conspire with the force of 

 his muscles, and to exhaust on the bar as much motion as 

 he can accumulate in a pull of three feet, in order to give il 

 a species of percussive effect. Hence the employment of 

 pulling at the common press has been always regarded a? 

 one of the severest kinds of labour ; nor has it been repre- 

 sented without reason as often " destructive of health and 

 life." 



It has long been an object with those interested in the 

 improvement of the art of printing, to introduce into the 

 press a variable power, which shall increase with the resist- 

 ance to be overcome, and thus render the pull on the bar a 

 nearly equable one throughout. The earliest contrivance 

 for this purpose which appears to have been in any degree 

 successful, was that of Mr. Roworth, a London printer.* In 

 his press the screw was dispensed with, and a plain spindle 

 substituted in its place. To the under side of the head o' 



* See art. Printing', Rees' Cjc. for a more full account of this coT}Pt.ructiot(. 



