40 Mr. J. N. Hearder on the Atlantic Cable. 



workmen employed, might fall very far short of what was ori- 

 ginally expected. Indeed the induction coil is an instrument 

 the success of which depends so much upon the experience de- 

 rived in the course of repeated manufacture, that the greatest 

 wonder is that Mr. Whitehouse's coils have succeeded at all 

 under such disadvantageous circumstances. They possess the 

 elements of enormous power, if judiciously arranged and con- 

 structed; but since they give such uumistakeable evidence of de- 

 fective construction, it would be hardly fair to attribute their 

 present failure to a faulty arrangement. I do not refrain, how- 

 ever, from stating my general objection to every portion of the 

 plan upon which they are made. One peculiarity in particular, 

 which renders them totally unfit for the purpose for which they 

 are intended, is that the secondary current is deficient in inten- 

 sity, and that its quantitative eflFects are not only far too great 

 for the required purpose, but the current itself, instead of being 

 abrupt and instantaneous, possesses an amount of duration quite 

 incompatible with the rapid reiteration of signals. In some ex- 

 periments which I witnessed, the secondary current, in passing 

 between large copper terminals, flowed for more than a second, 

 producing a vivid combustion, which pei'mitted the terminals to 

 be gradually separated from each other to a distance of three- 

 quarters of an inch. A current capable of flowing for so long a 

 time through such a resisting medium as the atmosphere, would 

 flow still longer through a conductor, and would thus add greatly 

 to the difficulties already presented, as I have shown by the con- 

 struction of the Atlantic Cable. 



In order to provide a current suitable for the capacity of the 

 enormous primary wires of these induction coils, gigantic batteries 

 were constructed, consisting of 400 plates of silver 9 inches 

 square, and the same number of similar plates of zinc, which 

 were fitted into 20 gutta-percha troughs, each containing 20 

 alternations of zinc and silver. The 20 silver and 20 zinc plates 

 in each trough were arranged as single pairs, all the silver being 

 united at the top, and all the zinc at the bottom. The whole 

 battery thus consisted of 20 pairs of plates, each containing 

 22 i square feet of silver, calculating both sides in action. These 

 stupendous batteries were mounted in ponderous iron girabels 

 for the sake of stability on board ship ; the cost of the silver was 

 about £2000, and that of the whole batteries, independently of 

 coils or other apparatus, about £3000. Subsequently, however, 

 from some experiments with plates of gas carbon, it was dis- 

 covered that these were more energetic in their action than silver 

 plates, and accordingly the electrician of the Company deemed 

 it advisable at once to discard all the latter, and introduce plates 

 of gas carbon in their place. 



