98 
Proceedings of the Royal Society 
a very peculiar texture, beiug close grained and black, and break- 
ing with a remarkable conchoid al fracture. This mine is situated 
in Eastern Siberia, on the Lower Tunguska, about 240 miles from 
its confluence with the Ye-nee-sey, its geographical position being 
between 50° and 65° N. Lat., and in 102° E. Long. 
The bank of the river for 1960 feet is formed entirely by a sec- 
tion of the graphite stratum, varying from 35 inches to 5 feet in 
thickness, and above it, often receding several feet, the stratum of 
spathose-iron ore, also about 5 feet in thickness. These beds of 
graphite and iron ore being washed by the river floods, are quite bare 
for from 30 to 105 feet inland, where a bank begins to rise, formed 
by the detritus of a mountain side ; one of the chain of Alexyef, 
which itself is placed about 1800 feet from the shore. This moun- 
tain is composed of gneiss, and it has not been ascertained whether 
either of the strata above mentioned pass into the mountain, but 
they have been traced nearly t 9 the base by borings, and have been 
found to extend, without varying very much in thickness, over a 
space of about 1960 square feet, computed to contain 12,000,000 
cubic feet of graphite. 
The author believes that no similar beds or strata of graphite 
have ever been discovered, this mineral usually being in imbedded 
masses, rarely very large, or in large nodules in pockets formed in 
trap and other igneous rocks. 
The third mine described — namely, that of M. Alibert — is of 
this character. It is also in Eastern Siberia, at the foot of Mount 
Balagool, 98° 30" E. Long., by 52° 20" N. Lat., 200 miles west 
from Irkutsk. Mount Balagool is composed chiefly of sienite, 
and it is by laborious operations that the graphite is raised to the 
surface. The mines are worked by the half-wild Buriates of the dis- 
trict ; but the quality of the graphite is so remarkably fine that it 
amply repays the labour, L.1200 worth having being raised in the 
first four months. 
The author called attention to these mines, because, from their 
vastness, as compared with other graphite deposits, they assume a 
geological importance, and are rendered peculiarly interesting by 
the facts lately stated by Dr Pauli respecting the development of 
plumbago in the process of manufacturing caustic soda on a large 
scale. 
