332 MEMOIR OF DANIEL TREADTVELL. 



" After studying with Dr. Ware about a year and a half, my health improved, and with it 

 my mind returned to its old habits of ranging upon mechanical operations. Examining the 

 various ways of applying the force of the muscles of the limbs to the motion of machines, and 

 being aware of the fact that in the human subject the lower extremities are vastly more 

 powerful than the arms, it occurred to me that this circumstance might be taken advantage 

 of in the construction of machines which are operated by human force, particularly when a 

 considerable expense of that force is required without any great accuracy in its immediate 

 direction. After some deliberation I selected the printing-press, as connected with one of our 

 most useful arts, and as well fitted to illustrate the principle assumed. On analyzing the 

 various actions of the common press, I became acquainted with other facts which confirmed 

 me in my choice. I found that in the common press two thirds of the power applied to 

 it was exhausted in conquering the elasticity of the materials of which it is made, and that 

 in the iron presses which have been recently introduced this elasticity, though lessened, is 

 still the cause of a notable loss of power ; for iron, and all materials of which a press can be 

 made, are more or less elastic ; besides this, the actual interposition of some very elastic body 

 between the platen and the types is absolutely necessary. Now, as the reaction of an elastic 

 body is equal to the force actually expended in its compression, it was obvious that, if a press 

 were made to operate by the gravity of the body, a power which acts without any fatiguing 

 muscular exertion, and gave the impression by a mere descent of the operator, such a press 

 would relieve him of an amount of exertion equal to the whole reaction of the elastic parts of 

 the press, and if the force which would then be required of him were obtained from the 

 muscles of the legs instead of those of the arms, I was confident that it would be improving 

 the press in an essential degree. It was these views of the case which led me to contrive a 

 frame, levers, and joint similar in principle and mode of action to those used in my present 

 press. I preferred the lever to any other mechanical power ; and for the ' toggle joint,' 

 through which the weight of the operator is communicated to the lever, it has the essential 

 advantage of becoming more powerful as it advances in its course, and that in a ratio nearly 

 corresponding, in the printing-press, with the increase of resistance. At this stage of the 

 invention I became aware of the advantages which would result from rendering the ' form ' 

 stationary. To accomplish this, one obvious mode would be to unite the platen with the 

 'tvmpan,' but some mode of counterbalancing the weight of the platen, other than by an equal 

 weight acting simply on the other side of the axis on which the platen rotated, must first 

 be contrived ; for if that mode were adopted, the platen and its counterbalance would take up 

 the slow oscillatory motions of the compound pendulum, besides having a great amount of 

 vis inertia, which must be overcome by the operator four times for each impression. In the 

 counterbalance which 1 have adopted, the force acts always in opposition to the weight of the 

 platen, and its velocity is so great that it can receive no impulse from the action of the platen 

 which shall essentially lessen its force. Still, however, it is desirable to make the platen as 

 light as may be, without in any way yielding or springing in taking the impression. My 

 contrivance for diffusing the pressure on various points of the platen, by means of numerous 

 bars arranged to form the skeleton of a pyramid, had this object in view, and enables me to 

 make a platen in every point as strong as the common platen with a much smaller quantity of 

 metal or wood. As to my contrivance for turning the sheet, experience proves it of some 

 importance in the economy of the time of the operator. There are various other moving 

 parts in my press which are new, or are not to be found in the common press. The motions 

 obtained from these are necessary, and whether they might be better obtained from some other 



