ELECTRIC TELEGRAPHS. 409 



congested. Accordingly, the cumbrous form of the double needle was 

 converted into the lighter and more rapid instrument that we have 

 here. 



This is the last and latest form of the double-needle instruments 

 used in England. It is still very largely employed on the railways, 

 but it is rapidly making its disappearance. It was very evident at 

 once that if it were possible to form the letters of the alphabet by the 

 combinations of the motions of the needle to the right or left, that it 

 was quite possible to form such an alphabet by means of one needle 

 in fact, there is no doubt that the very first needle telegraph ever in- 

 vented, that of Schilling, was based upon a combination of the move- 

 ments of the needle to the right and the left. Here we have the first 

 form of needle instrument so introduced. We have a single needle 

 which by its deflections to the right or left would form an alphabet : 

 one motion to the left, one to the right, the letter " a ;" one to the 

 right and three to the left, the letter " b," and so on ; by the combina- 

 tion in that way the letters of the alphabet are formed. 



This is a second form of a needle instrument of the same kind, and 

 this is the form that is used in the present day. These instruments 

 are very largely employed at some of our smaller post-offices ; and 

 they have one great merit about them extreme simplicity and the 

 avoidance of the necessity of employing skilled clerks. Very little 

 instruction, very small pay, induce clerks speedily to acquire a know- 

 ledge of the single needle. 



Now, as we progress in telegraphy, speed has become an essential 

 quality. The first instruments, the four-wire and the double-needle 

 seen here, were made of galvanometer coils of great depth and magnets 

 of great length, their form necessarily became sluggish and cumbrous. 

 The first to make any alteration in that direction was Mr. Holmes, 

 who succeeded in reducing the six-inch needle to this little diamond- 

 shaped form, and by the simple reduction of the size the speed of the 

 instrument was at once increased nearly fourfold. We have by various 

 alterations and suggestions and additions, arrived now at the form of 

 needle which I hold in my hand, and with this needle the motions can 

 be made so rapidly that the eye can scarcely follow them. Now, as 

 you have perceived, these instruments are simply transitory in their 

 signals. 



