8 ON THE COMMERCIAL KINDS OF INDTA-RUBBER. 
in all the specimens examined, I have invariably found the centre un- 
changed in colour, and no trace whatever of any fuliginous deposit 
between thelaminz. Frequently I have cut off all the exterior portions 
of a piece of this kind of rubber, and have noticed how soon the cut 
edges assume the browny tinge on exposure. 
There are three or four forms in which we receive Para caoutchouc 
in this country ;—1st, flat pouches, called biscuit; 2nd, the well-known 
bottles; 3rd, Negrohead ; and 4th, scrap. The ^ biscuit” consists of 
all the fine rubber, carefully prepared, It is made in the same manner 
as bottles, by successive dipping,—thus showing a beautifully-even, 
laminated appearance. The necks are very narrow, thus necessitating 
cutting the sides to let the mould out. The ** Negrohead " consists of 
ali the “scrap” left after the preparation of the fine, rolled into very 
large balls or blocks, sometimes about twelve inches in diameter. 
These offer an excellent opportunity for adulteration, which the In- 
dians are not slow to avail themselves of. Sometimes a large piece of 
clay is found in the centre; and in one specimen, now at the Kew 
Museum, I found inside one or two rings of earthenware, a mass of 
roots, and a textile substance in the centre, 
The value of the imports of Para rubber in 1866, as per customs 
lists, was £381,461; in 1865, £348,712; in 1864, £307,923 ; in 
1863, £299,641. The lowest price ever paid is said to have been 
Tad. per lb., but now it is about 2s. 27. In 1866, the price ranged 
from 3s. 1d, to 1s. 84d., according to the stock and demand. 
In January, 1866, I obtained a sample of india-rubber from Demerara, 
in the shape of small round bottles and balls. This is very much like 
the Para rubber; and as Demerara is mentioned by Dr. Lindley as one 
of the habitats of Hevea Guayanensis, Aubl., it is, in all probability, 
produeed by it. However, it should not be forgotten that one 
other plant is mentioned as yielding caoutchouc in Demerara, viz. 
Tabernemontana utilis, Arnott, called by the natives Hya-Hya. It 
is described by Arnott as “yielding a copious stream of thick, rich, 
milky fluid, destitute of all acrimony, and only leaving a slight clam- 
miness on the lips. A tree felled on the banks of a small stream com- 
pletely whitened the water in an hour or two.” Dr. Christison found 
the milk to contain a small proportion of caoutchouc, and a large 
proportion of a substance of a nature between caoutchoue and the 
resins, 
ee 
