56 A NEW THEORY OF EVOLUTION. 



is an ordinary loom), that, by means of per- 

 forated pasteboard cards affixed to the face 

 of a cylinder (so called), automatically guides 

 the threads of the warp to throw up a 

 designed pattern. The cylinder revolving, 

 presents successively to the mechanism a 

 series of cards, perforated to produce a cer- 

 tain design, and by means of the perfora- 

 tions the mechanism is guided to throw up 

 the pattern they represent. To change the 

 pattern, it is necessary to replace only such 

 cards as would conflict with the new design, 

 by others suitably perforated ; the other 

 arrangements of the loom may remain un- 

 changed. 



Thus if a Jacquard loom has been weaving 

 damask tablecloths having a plain border, 

 surrounding a twilled square, with a flower 

 pattern within a disc in the centre, and the 

 loom is required to manufacture a similar 

 tablecloth, but with a pattern of shells in 

 the disc instead of flowers, it would only 

 be necessary to substitute fresh cards, per- 

 forated to produce shells instead of flowers, 

 for the cards whose perforations would con- 

 flict with the new pattern. The loom, with 

 the new cards adjusted on the cylinder, 

 would begin to weave the border of this 

 new tablecloth like the old, and also the 



