4 DIAMOND. 
adjacent plain began to be searched to the depth of 
from ten to fourteen feet ; and the work was, at one 
time, so extensively pursued, that nearly 6,000 persons 
were employed in it. At Soumelpour the diamonds 
are found amongst the sand and gravel of the river. 
Diamonds are likewise found in the island of Borneo, 
and in several parts of South America. The mode by 
which they are obtained from one of the rivers of 
Brazil has been described by Mr. Mawe. The current 
is turned, and part of the bed of the river being laid 
dry, the mud is taken up and washed, by negroes, in 
places prepared for the purpose, through which a por- 
tion only of the stream is allowed to flow. As soon as 
all the earthy particles have been washed away, the 
gravel-like matter that remains is raked together, the 
stones are thrown out, and what diamonds happen to 
be present are found amongst the refuse that is left. 
To ascertain whether a stone, that has been found, 
be really a diamond, the workmen have a mode of 
placing it upon a hard substance, and striking it with 
a hammer. If it either resists the blow or separate into 
leaves, it must be a diamond ; but, in the latter case, 
the discovery is sometimes made at an immense ex- 
pense, as, by thus diminishing the size, its value must 
also, of course, be greatly diminished. 
Diamonds are generally exported from Madras in a 
rough state ; and in small parcels neatly sewed in mus- 
lin, and sealed by the merchants who send them. 
These, we are informed by Mr. Milburne in his valu- 
able work on oriental commerce, are, for the most 
part, sold in Europe by the invoice, as it is called ; that 
is, without being opened : and he says that they are 
always found to contain the value for which they were 
sold in India. 
Of all transparent substances, none for brilliancy- 
can be compared with the diamond. Its hardness is 
such, that no steel instrument whatever can make any 
impression upon it. Notwithstanding this, at a tem- 
perature not so high as that which is required for the 
