458 
BITUMEN. 
is of various depths, from two to ten feet, and the 
channels are continually fluctuating; one of eight 
or ten feet to-day, may to-morrow be entirely closed 
up, and others formed where yesterday was a solid 
mass of pitch. From this Mr. Tobin thinks it evi- 
dent that the asphaltum itself is supported by a lake 
of water underneath, but he is unable to form any 
idea of the thickness or substance of the stratum of 
bitumen. 
Asphaltum and maltha were both used by the 
Egyptians, mixed with the resin of the cedar, in 
embalming their dead bodies ; and it is observed, 
that the mummies are strongly impregnated with 
these materials even to the centre of the bones. 
There is still another kind of bitumen which 
may be mentioned in this place, though very dif- 
ferent in some of its properties from those we have 
already mentioned. Magellan calk it elastic petrol, 
Kirwan mineral caoutchouc, and Brogniart elastic 
bitumen. The properties which it possesses, in 
common with other bitumens, are its strong smell, 
particularly when soft; its tendency to inflamma- 
bility, and its being light enough to swim on water; 
but it differs essentially in its texture, and is so elas- 
tic that it can hardly be distinguished from Indian 
rubber, having the same property of removing the 
traces of a black lead pencil from paper. It is found 
in the same places as petroleum, that is, among 
spars and lead ores, either in lumps, or in a cylindrical 
form, like bits of thin branches or stalks of vegetables. 
