34 Mr. J. N. Hearder ou the Atlantic Cable. 



twisted together, forming a strand or cord about equivalent in 

 mass and conducting power to a copper wire of No. 15 or 16 wire- 

 gauge, the size of tolerably stout bell wire. This is not so thick 

 as would be used ou overland lines if copper were employed 

 instead of iron. Now even with the best insulation, and the 

 most favourable conditions of which these overland wires are sus- 

 ceptible, it is found that currents of high intensity are constantly 

 required in long lines ; yet it appears extraordinary that this fact 

 should have been overlooked in the determination of the size of 

 the Atlantic wire, placed as it is under conditions which tend to 

 divert the electrical effects of the currents through every inch of 

 its length. 



In addition to the great intensity of current requisite to over- 

 come this unprecedented amount of resistance, a still greater 

 degree of electrical force was necessary to compensate for the 

 absorbing or inductive influence of the insulating coating in close 

 contact with its surface. 



To meet this difficulty Mr. Whitehouse contrived his induction 

 coils, with a view of obtaining from their secondary currents 

 electricity at a degree of tension which should be adequate for 

 all the requirements of the cable. Unfortunately these coils, of 

 which I shall have to speak hereafter, were constructed upon 

 principles purely hypothetical, and were not the result of the 

 experience derived from practical investigation, or carefully and 

 gradually developed plans. 



The disadvantages arising from this attenuated form of con- 

 ductor are as follow : — 



1st. Its great resistance requires the employment of electricity 

 of very high tension, involving either the use of batteries in very 

 extensive series, or of electro-magnetic or magneto-electric ma- 

 chines of great power. 



2nd. Supposing the fii'st difficulty to be overcome, which is 

 quite practicable, another disadvantage presents itself, viz. the 

 necessity of adapting the recording instruments to the character 

 of the current. Electrical effects are of two kinds, designated 

 by the terms static and dynamic, embracing the two extremes 

 of intensity and quantity. Magnetic effects depend upon the 

 dynamic or quantity character of the current, and when they are 

 required to be produced from statical electricity, or intensity 

 currents of low dynamic character, they can only be obtained by 

 multiplying a great number of statical effects, so as to get the 

 united actions of the minute quantity due to each. 



Since with a long attenuated conductor, currents of high ten- 

 sion alone are available, the recording instruments must be such 

 as to be influenced by statical or high-tension electricity ; and 

 the result is, that in proportion as they are so, they ai'e not only 



