JDLr 1, 1865.] THE TECHNOLOGIST. 



THE TELEGRAPH. 541 



We had to wait, however, twenty years longer, till two famous 

 additional discoveries were made, the one that the electrical current de- 

 flects the compass-needle, the other that the electrical current developes 

 magnetism. Our earliest electric telegraph, and to this day the majority of 

 telegraphs are electro-magnetic ; in other words employelectricity to pro- 

 duce signals, either by moving a permanent magnet, or by making a tem- 

 porary one. 



But one statement needs be added. The land telegraph was now in 

 essentials complete, but a sub-aqueous telegraph was still impossible for 

 want of a- good insulator. Great historical importance, accordingly, 

 attaches to the importation, in 1843 of gutta-percha, which enabled us 

 to have a submarine cable as early as 1850. 



On the submarine telegraph I will only say that the peculiar electrical 

 difficulties which have vexed the Atlantic cable engineers, arise from 

 our having as it were stumbled again, as our forefathers did in 1745, on 

 the Leyden jar. They were trying to electrify water, and in so doing, 

 converted unwittingly, and much to their astonishment, a wet bottle 

 into what we now call a Leyden jar. We were trying to cross water 

 electrically, and as unwittingly converted a wet wire into a Leyden jar. 

 But the explication of this second Leyden arrangement is likely to do 

 as much for submarine telegraphy, as that of the first did for the land 

 telegraph. 



In spite however of all difficulties, we have done wondrous things 

 already with our telegraph, and we need not be surprised nor lose heart, 

 if we have to make as many voyages as Columbus did, before we rival 

 him in bringing the old and new worlds together. 



Let me offer you two feebly outlined word pictures of events which 

 were transacted on the same arena, at the interval of nearly four centu- 

 ries. The epoch of the first is the autumn of 1492. The scene is the 

 mid- Atlantic, and on its bosom floats the frail caraval of Columbus. It 

 is midnight, and the astonished pilots are gazing with awe on the com- 

 pass-needle which has ceased to point to the north-star, and has veered 

 round to the west, and they ask the great admiral what this unheard-of 

 variation may mean. To him it is a mystery as well as to them, but he 

 has an explanation which contents them, and for himself, however 

 mysterious it may be, it is anew the finger of God bidding him sail west- 

 ward still, and he follows its new pointing, till it lands him on the shore 

 he has so often seen in his dreams. 



The time of the second picture is 1858, the scene as before, is the mid- 

 Atlantic, and on its bosom a great English steam-ship is silently gliding 

 with every sail furled. It is midnight again, and the sailors, as in the 

 caraval four centuries ago, are gazing with intense eyes upon a quiver- 

 ing needle. It is not however, a mere compass-needle ; but armed with 

 a tiny mirror, it lies in the centre of a coil of wire looped to the great 

 cable which, as electric signals pass along it, is every moment bringing 

 the old and new worlds nearer each other in time. Every quiver to east 



