Royal Institution of Great Britain. 553 



The process of bleaching; has mainly contributed to the improve- 

 ment in the quality of paper, while the paper machine, the principal 

 object this evening-, has secured economy of production. 



The machine in general use for making- paper was introduced by 

 Messrs. Fourdrinier; it was first suggested by M. Didot, (not the 

 celebrated printer), but his plans were too crude for practice, and 

 the machine received its perfection from Mr. Donkin. It consists 

 of an endless web of wove wire, about thirty feet long in the web, 

 or * wire,' as it is called, and joined together after the manner of 

 a jack-towel ; the endless wire runs over a number of rollers, placed 

 horizontally, so as to present a level surface abput fifteen feet long: 

 as the wire moves, a quantity of pulp is allowed to flow upon it 

 from a chest, or vat, at one end of the wire ; this chest is furnished 

 with a broad and level spout extending across the wire ; the spout 

 has an apron or slip of leather nailed to it, so that the leather 

 apron lies upon the wire and prevents the pulp from running off, 

 while the flexibility of the leather allows the wire to move under it 

 without injury. A shaking or jogging motion is given to one end 

 of the wire to produce the felting of the floating fibres, and the 

 water continues to drain from the pulp till it reaches the further 

 end of the wire : here the water is more completely pressed out by 

 rollers; the web of paper may then be considered in form; it is, 

 however, too weak to support its own weight, and is passed over an 

 endless cloth, in order to expose it to the air, to soak out still more 

 moisture, and to make the texture firmer by passing it between other 

 pressing rollers ; it is then passed over large cylinders filled with 

 steam, which effectually dries it, and the web of paper is finally 

 wound round a reel, which will thus sometimes contain a single 

 sheet of paper three-fourths of a mile long. 



Beautiful and striking as this machine is, it is yet exceeded by 

 the machine invented by Mr. Dickinson. Instead of the endless 

 web of wire thirty feet in length, he employs a perforated brass 

 cylinder, about twenty inches diameter, covered with the woven 

 wire. The cylinder revolves in a vat of pulp, in which it is so far 

 immersed as to leave about one foot4bf the surface of the cylinder 

 above the surface of the pulp. As the cylinder revolves, the water 

 flows through the wire into the interior of the cylinder, whence it is 

 abstracted by a syphon passing through its hollow axis, and the 

 pulp continues to accumulate upon the whole immersed surface of 

 the cylinder. At that part of the cylinder which is not immersed in 

 the pulp, the action of an air pump is most ingeniously applied ; 

 a pipe from an air pump is introduced through the hollow axis of 

 the cylinder, and terminates in a pan or trough fitted close by 

 * packing' to the interior of the unimmersed part of the cylinder; this 

 air trough maintains its position while the cylinder revolves over it, 

 and the instant the unformed paper comes over the air-trough, the 

 water passes through and the paper is set : it is subsequently passed 

 between pressing rollers, and dried by steam, and reeled up as al- 

 ready described. 



