272 Professor Faraday, [June 8, 



of the design ; and in the Jacquard loom, each of these required a card 

 pierced in a certain order, which being brought against the ends of a 

 set of horizontal rods, allowed some to remain undisturbed, whilst 

 others were pushed on one side. By the action of the pedal the warp- 

 threads associated with the undisturbed rods were raised and those 

 belonging to the displaced rods were left unmoved ; and to do this 

 rightly, a separate pierced card was required for every thread that 

 crossed the warp within the extent of the pattern. Frequently some 

 thousands of cards are needed, and for the production of a woven 

 portrait of M. Jacquard, in black and white silk, as many as 24,000 

 were employed. 



After a design has been decided upon, it has to be converted into 

 these cards, one for each thread of the weft included in the design ; 

 the preparation and piercing of them requires much care and time, 

 after which they have to be linked together as an endless chain in 

 their proper order. It is to replace this part of the weaving arrange- 

 ments that Mr. Bonelli has applied his attention, and the peculiar 

 power of electricity. Instead of the many pierced cards, he has but 

 one card, or rather its equivalent, a convertible plate of brass ; which 

 being pierced with the full number of holes required (which in the 

 loom in action was 400) can have these holes either stopped or left 

 open so as to represent by its successive changes of condition the suc- 

 cessive cards of the Jacquard series. To obtain this effect, tin foil is 

 attached strongly to paper, so as to form a compound sheet. The 

 design is then drawn upon the metallic surface with black bituminous 

 varnish, and the sheet is made into an endless band, which being placed 

 upon a roller, and kept in its position by stops, moves as the roller 

 moves, being carried forward by its motion. A set of teeth rests upon 

 the top of this roller, touching the pattern in a line ; they are made of 

 thin brass plate, so thin that 400 of them do not occupy more than 16 

 or 1 7 inches, i.e. the width of the design on the roller ; yet so separate 

 that each is insulated from its neighbour by little interposed teeth of 

 ivory ; and so large and therefore weighty as to fall and rest upon the 

 pattern, making good electrical contact where the tin foil is exposed, 

 but being insulated where the bituminous pattern intervenes. 



Behind these teeth are 400 small electro-magnets fixed in a frame- 

 work, parallel to each other, and insulated. The fine covered wires 

 which constitute their helices are connected at one set of ends with 

 the teeth just described, each with a tooth ; whilst the other ends are 

 brought together and made fast to one metallic plate and wire. 

 Tracing this wire onwards, it comes to an interruptor or contact-maker 

 from whence the metallic communication proceeds to a screw appointed 

 to communicate with one end of a five-celled Bunsen battery, the other 

 end of which communicates with a screw near the former. This screw 

 has a wire proceeding from it to two insulated teeth, like the teeth 

 bearing upon the pattern, but heavier ; and these rest upon the un- 

 covered edges 5f the tin foil at the sides of the pattern, so as to keep 

 up a constant electric communication with it. By simple but perfect 



