PROCEEDINGS OF THE POLYTECHNIC ASSOCIATION. 941 



ranean. Experiments with various iion-conductiiig substances 

 were extensively made, but with respect to submarine and subter- 

 ranean lines, without any satisfactory practicable result with any 

 of them, except gutta percha. A brief notice of this valuable sub- 

 stance is here given. 



Gutta Percha 

 Is the Malagan term given to a concrete juice taken from the 

 Isonandia or gutta tree, indigenous to all the islands of the East 

 Indian Archipelago. The juice consolidates quickly after it is col- 

 lected, forming a compact mass, in hardness somewhat similar to 

 wood. 



Gutta percha is one of the best of the non-conductors of elec- 

 tricity, while its adaptability as a covering for submarine and 

 subterranean telegraph wire as an insulator, is unrivalled. It is 

 not injured by coming in contact with oil or other ftitty substances. 

 It resists the action of sulphuric, muriatic, and nearly all the other 

 acids. 



In the above properties it is the opposite of India rubber. 

 Gutta percha has an exceedingly line grain, and its oily property 

 makes it perfectly impervious to liquids. When exposed to the 

 action of boiling water it becomes soft like dough or paste, and 

 may then be moulded or worked to any shape, which shape it will 

 retain when cold. 



It will be observed that in the foregoing: remarks on jjutta 

 percha as an insulator, reference is made only to submarine and 

 subterranean lines. For these from its imperviousness to moisture, 

 its strength, durability and excellent power of protecting the wire, 

 it has assumed the supremacy over all other substances now 

 known. 



This substance was discovered by Dr. Montgomerie, at Singa- 

 pore, in 1822. The first importation of gutta percha into Europe 

 as an article of commerce, was to England, in 1842. Its first 

 importation into America was in 1847, by Wm. S. Wctmore, for 

 Samuel T. Armstrong, to manufacture. 



In its hard condition gutta percha is easily softened by heat, 

 and soluble by chloroform, &c. Many efforts were made to adapt 

 it in solution to the purpose of telegraphic insulation, but without 

 practical success. All the patents taken out for this purpose were 

 consequently valueless, until, in England, a method was devised 

 which was completely successful. Availing himself of the sus- 



