ON THE VARIOUS APPLICATIONS OF GUTTA PERCHA. 319 
Crane (chemist to the Gutta Percha Company,) found it in 
its ordinary state to consist of at least two distinct materials, 
besides a notable proportion of sulphur — viz.: 1. A white 
matter, gutta percha in its pure state; 2. A substance of a 
dark-brown colour. Various experiments were made to 
ascertain its strength when mixed with other matters, and 
also as to what pigments would mix with it without ren- 
dering it brittle or deteriorating its qualities. From these it 
appeared that the only pigments that could be altogether 
relied on to be used with gutta percha were orange lead, 
rose pink, red lead, vermilion, Dutch pink, yellow ochre, 
and orange chrome. Under the influence of heat and pres- 
sure, gutta percha would spread to a certain extent, and 
more so if mixed with foreign matters. All the mixtures 
composed of gutta percha and other substances which had 
been subjected to experiments, except thatcontaining plum- 
bago, were found to increase its power of conducting heat ; 
but in its pure state gutta percha was an excellent non- 
conductor of electricity. The best composition for increas- 
ing the pliability of gutta percha was that formed in con- 
junction with caoutchouc tar, and next in order that of its 
own tar; and the best material at present known for mould- 
ing and embodying, was obtained by mixing gutta percha 
with its own tar and lamp black. In describing the process 
of manufacturing gutta percha, the author observed, that 
rude blocks of the material were first cut into slices, by 
means of a cutting machine formed of a circular iron plate 
of about five feet in diameter, in which there are three radi- 
cal slots furnished with as many knives or blades. The 
blocks are placed in an inclined shoot, so as to present one 
end to the operation of the cutters. The slices are then 
placed in a wooden tank, containing hot water, in which 
they are left to soak until found in a plastic state. They 
are afterwards passed through a mincing cylinder, similar 
to that used in paper mills for the conversion of rags into 
pulp, and then thoroughly cleansed in cold water tanks ; the 
