352 



3Ir. Francis Gallon 



[May 25, 



of parallel strings or wires, one for each measure, that are stretched 

 between Rods and across Bridges at either end of a long board set 

 cross-ways to the cards. Their positions on the bridges are adjusted 

 by the same scale as that by which the notches were cut in the cards. 

 Figs. 6a and 66 are views of this portion of the apparatus, which acts 

 as a key, and is of about 30 inches in eifective length. The whole is 

 shown in working position in Fig. 7. When the key is slid into its 

 place, and the heavy end of the tilting-frame T is raised, all the cards 

 are free to descend so far as the tilting-frame is concerned, but they 



Fig. 6a. 





I i 

 I I 



! i 



I K I 



K 



Plan and section of the key-board K. 



are checked by one or more of the wires from descending below a 

 particular level, except those few, if any, whose notches correspond 

 throughout to the positions of the underlying wires. This is the case 

 with the card c2 (Fig. 5), drawn with a dotted outline, but not with cl, 

 which rests upon the third wire, counting from the axis. As the wires 

 have to sustain the weight of all or nearly all the cards, frequent narrow 

 bridges must be interposed between the main bridges to sustain the 

 wires from point to point. The cards should be divided into batches 

 by partitions corresponding to these interposed bridges, else they may 

 press sideways with enough friction to interfere with their free indepen- 

 dent action. Neither these interposed bridges nor the partitions are 

 drawn in the figure. The method of adjusting the wires there shown, 



