MANUFACTURES.

31

Manu- nation is not without considerable difficulties, for although the converse operation of Sect. i.taking an impression from a liquid surface has a parallel in the Art of marbling paper,the possibility of transferring the ink from the copper to the fluid requires to be proved.

Another and more plausible explanation is founded on the elastic nature of the com- Second

. , , # explanation.

pound of glue and treacle, a substance already in use in transferring engravings toearthenware. It is conjectured, that an impression from the copper plate is taken upona large sheet of this composition; that this sheet is then stretched in both directions,and that the ink thus expanded is transferred to paper. If the Copy is required to besmaller than the original, the elastic substance must first be stretched, and then receivethe impression from the copper plate: on removing the tension it will contract, and thusreduce the size of the design. It is possible that one transfer may not in all casessuffice, as the extensibility of the composition of glue and treacle, although consider-able, is still limited.

Perhaps sheets of Indian rubber of uniform texture and thickness may be found toanswer better than this composition. As it would require considerable time to produceimpressions in this manner, and there might arise some difficulty in making them all ofprecisely the same size, the process might be rendered more certain and expeditious, byperforming that part of the operation which depends on the enlargement or diminution.of the design only once ; and, instead of printing from the soft substance, transferringthe design from it to stone: thus a considerable portion of the work would be reducedto an Art already well known, that of Lithography.

We shall terminate this enumeration, which is far from complete, of the Arts in which instanceCopying is the foundation, with an example which has long been under the eye of our pii™ ’readers, although few, perhaps, are aware of the great extent of repeated Copying of Copy,ng 'which these very pages are the subject.

1. They are Copied by Printing from stereotype plates.

2. These stereotype plates are Copied, by the Art of casting, from moulds formedof plaster of Paris.

3. Those moulds are themselves Copied by casting the plaster in a liquid state uponthe movable type set up by the compositor.

[It is here that the union of the intellectual and the mechanical departments takesplace. Through how many stages of repeated Copying the matter which is here deli-vered to the reader may have travelled, we shall leave involved in a veil which his saga-city may penetrate; merely observing, that in numerous instances the mental far outrunsthe mechanical Copyist.]

4. These movable types, the obedient messengers of the most opposite thoughts,the most conflicting theories, are themselves Copies, by casting from moulds of coppercalled matrices.

5. The lower part of those matrices, bearing the impressions of the letter or characterintended, are Copies by punching from steel punches on which the same character existsin relief.