202 Mr. Grace Calvert^ on the Influence of Scie9ice [Feb. 17, 



softened steel, of the necessary dimensions. This roller is then hard- 

 ened and introduced into a press of peculiar construction, where, by 

 rotatory pressure, it transfers its design to a similar roller in the soft 

 state, and the die being in intaglio, the latter, called the " mill" is in 

 relief. This is hardened in its turn, and by proper machinery is made 

 to convey its pattern to the full-sized copper roller. This improve- 

 ment alone reduced the cost of engraving on copper rollers many 

 hundreds per cent. ; and, which is of far greater importance, made 

 practicable an infinite number of intricate engravings which could 

 never have been produced by hand labour applied directly to the 

 roller. 



A further improvement was made by tracing with a diamond on 

 the copper roller, covered with varnish, the most complicated patterns 

 by means of excentrics, and then etching. 



The combination of mill engraving with the tracing and etching 

 processes naturally followed, adding immensely to the resources of the 

 engraver and printer in production of novel designs. 



Another development of this art is the tracing of patterns on the 

 surface of rollers, which has been effected by machines constructed on 

 the principle of the pentagraph. Although this invention dates from 

 1834, still it is only of late years that it has been successfully applied. 



But if mechanical art has greatly assisted the engraver, chemistry 

 has rendered him equally important services, by enabling him to 

 abandon costly and cumbrous modes of impressing by force the designs 

 on the cylinder, substituting for them a great number of etching pro- 

 cesses. By some of these processes, as by every other addition to the 

 resources of the engraver, an entirely new and beautiful class of en- 

 graving is produced, unattainable by any other known means. 



A very recent improvement is highly interesting in a scientific 

 point of view. It is the application of galvanism to the diamond 

 tracer. By combining the galvanic action with the excentric motion, 

 most beautiful and delicate engravings can be produced. This is 

 effected by tracing the pattern with a varnish on a zinc cylinder, 

 which is so placed in the engraving machine, that as a needle passes 

 over its surface, and comes in contact with the zinc, the galvanic current 

 is established, and by simple machinery, causes the diamond to trace 

 the corresponding pattern on the copper roller. The communication 

 is so rapid and so precise, that this invention of Mr. Gaiffe, of Paris, 

 bids fair to produce very important results. Galvanism is also made 

 use of, for producing effects on roller surfaces by depositing copper 

 thereon. 



To give an idea of the extraordinary influence which the intro- 

 duction of machinery and improvements in engraving have had 

 in cheapening the cost of printed calicoes, I may state, that large 

 furniture patterns, such as are required for Turkish, Egyptian, and 

 Persian markets, into which 16 colours and shades enter, would have 

 cost formerly, from 30*. to 35*. per piece, because they would have 

 required 16 distinct applications of as many different blocks, and 



