INDIA RUBBER AND GUTTA-PERCHA. 689 



works upon the subject.) Nor was it until January 10, 1849, some 

 months later, that Walker, one of the first savants that busied them- 

 selves with electricity, and who first experimented with the rail- 

 way block- system, successfully telegraphed in the harbor of Folke- 

 stone on what is generally considered the first submarine cable. 

 It was a gutta-covered cable extending from a boat two miles to 

 the shore. The favorable results at Folkestone encouraged John 

 W. Brett, who is known in England as the father of submarine 

 telegraphy, to construct the first long line from Dover to Calais, 

 with the encouragement of the French Government, in 1850, 

 when the successful application of gutta-percha to real submarine 

 telegraphy was demonstrated and Wheatstone's hopes were com- 

 pletely realized. Brett labored with great energy for the success 

 of long-distance submarine communication, and his faith and ad- 

 vice, as well as capital, were of the very greatest value to Field 

 and his fellow-promoters of the first Atlantic cables. In 1851 the 

 fire-hose at the exposition in London was of this substance, and 

 on the last voyage in search of Franklin a light and portable 

 gutta-percha boat did good service, showing that the material 

 was suitable for the sheathing of boats. Advantageous use was 

 also made of it in making molds for reproducing delicate impres- 

 sions in the galvanoplastic process. But, except in telegraphy and 

 galvanoplasty, its employment soon diminished. Shoes of gutta- 

 percha softened before the fire and stuck ; clothing made of it in 

 turn fell into ill favor. Vulcanizing and mixing with rubber 

 were thought of, but still satisfactory products were not obtained. 

 They were hard and were soon abandoned. 



The failure of gutta-percha for some purposes is owing to its 

 greater suppleness at a slightly elevated temperature. It may be 

 vulcanized by adding sulphur and heating to 135 to 150 C, but 

 this process, owing to inconvenient results obtained, is now very 

 rarely employed. Its resistance to acids led to its being put to 

 use for vessels and tubes in factories of chemical products and 

 laboratories, while medical science, as seemed promised at its 

 coming, has found in it a valuable auxiliary. 



The gutta-percha of commerce contains impurities wood, 

 earth, sand, etc. which must be eliminated. It may be dissolved 

 in sulphide of carbon or benzene. Then decant and allow to 

 evaporate. A cheaper and preferred method is by mechanical 

 means. The cakes are cut into chips, which are plunged into a 

 hot- water vat and stirred by an agitator ; the heavy substances 

 go to the bottom, the gutta and wood remaining on top. A series 

 of rasps removes the wood, and the gutta is taken and dried. The 

 process is often accomplished by still other machinery for remov- 

 ing the foreign substances, care being taken to squeeze out all 

 the air bubbles. The gutta is now pure, but may be mixed witl^ 



^OL. L. 53 



