940 TRANSACTIONS OF THE AMERTCAN INSTITUTE. 



Avbich bad been under salt water, in Miiskcgat channel, five years. 

 The teredo bad eaten tbe pine wedge, but tbe gutta percha was 

 uninjured ; showing that this most destructive sea-worm, which 

 destroys ship's bottoms, timber, and everything in its way, will 

 not eat gutta percha. All experience shows fully, the perfect 

 indistructabilit}' of gutta percha under water, and even under 

 ofround, when properly laid and protected from tbe action of tbe 

 sun, heat and atmospheric changes. Speaking of telegraphing 

 across the ocean, on page 487 of American Institute Transactions 

 for 1864, Dr. E. P. Stevens says : "At tbe present time the ocean 

 contains salts of copper and acids that will affect the metal cover- 

 ing of tbe wire, and the vegetable matter, such as the hemp and 

 gutta percha, used in its construction, must sooner or later be 

 destroyed." Experience has since shown that gutta percha will 

 not decay under water. Mr. B. P. Finnell, see page 488, same 

 book, exhibited a piece of the first Atlantic cable from on board 

 steamship " iV^mya/'fl," and since kept in a damp place, tbe gutta 

 perclia was found to be shrunk half an inch in the piece eight 

 inches long ; and the effects of this on a cable of some miles in 

 length was obvious." 



In answer to these statements, Mr. Bishop exhibited two pieces of 

 submarine cable made V)y him about four years ago, which have been 

 exposed to the atmosphere ever since. One of these, about twelve 

 inches long, is shrunk about one-quarter of an inch on each end, 

 where it was exposed ; but tbe other piece, about ten inches long, 

 which was varnished on tbe ends where the gutta percha was 

 exposed, was not shrunk at all, showing that it is on]y where the 

 atmosphere attacks gutta percha that it shrinks ; and that in a 

 cable protected by a hemp and tar bedding, where the almosphere 

 is entirely excluded, there cannot be any shrinkage or injuiy to 

 the insulation, and if under water beside, it is beyond tbe reach 

 of harm. 



The following may not be uninteresting in this connection : 

 The history of Prof. Morse's experiments and their I'csult, the 

 grandest and most wonderful discovery in the arts of modern 

 times, need not be here recapitulated. Tbe discovery of some 

 efficient and practical non-conductor to shield the wire from con- 

 tact with other conducting sul)stances, and prevent the escape from 

 it of the electric fluid on its wa}' to its destined point, now became 

 a desideratum of the highest, and indeed of vital importance to the 

 success of telegraphic lines, whether aerial, submarine or subter- 



