THE TECHNOLOGIST. [Aug. 1, 1865. 
12 SUBSTITUTES FOR GUTTA-PERCHA. 
habit of the New Caledonian species, the tree being conical, the tiers of 
"brandies perfectly regular, and having a slight droop at their tips, 
cut a spar of it on Magnetical Island, to make a top-mast, and the 
wood was hard and close-grained, paler than that of the Moreton Bay 
pine, and would not swim. It produces a white resin abundantly." — 
' The Intellectual Observer.' 
SUBSTITUTES FOR GUTTA-PERCHA. 
The forests of British Guiana yield caoutchouc and a variety of gums 
of allied nature. Sir W. H. Holmes, of Georgetown, when com- 
missioner in London at the Exhibition of 1862, drew prominent atten- 
tion to a new insulating material possessing properties intermediate 
between those of caoutchouc and gutta-percha. 
" It is the dried juice of the bullet tree (Sapota Mulleri), and is 
called Balata. It appears likely to be more valuable than india-rubber 
or gutta-percha by themselves, as it possesses much of the elasticity of 
the one and the ductility of the other, without the intractibility of india- 
rubber, or the brittleness and friability of gutta-percha, whilst it requires 
a much higher temperature to melt or soften it. . . . There appears 
to be every probability that balata will become an important article of 
commerce, supplying the great want of the day — a good insulating 
medium for telegraphic purposes. Professor Wheatstone is now investi- 
gating its electrical and insulating properties. Another substitute for 
gutta-percha, the juice of the Alstonia scholaris, a tree belonging to the 
natural order Apocynea, has been forwarded from Ceylon by Mr. 
Ondaatjie ; it is stated to possess the same properties, and to be as 
workable as gutta-percha. It readily softens when plunged in boiling 
water, is soluble in turpentine and chloroform, receives and retains 
impressions permanently, and is adapted for seals tc documents. These 
specimens are sent in response to premiums offered by the Society of 
Arts for the discovery of a subsitute for gutta-percha." 
Although several of this class of gums differ but slightly in chemical 
composition, it is well known that they are possessed of very different 
properties. For example, gutta-percha becomes plastic when immersed 
in hot water, a property not possessed by caoutchouc. Again, while the 
latter can be extended with facility in all directions, the former admits 
of extension only in the direction of the fibre or grain. Caoutchouc 
seems impermeable to water, even under great pressure and elevated 
temperature, while gutta percha is of a somewhat porous nature and not 
so well adapted to the purpose of insulation in the construction of sub- 
marine telegraphs. This fact appears to have been established by the 
Messrs. Silver, of Silvertown works. 
