42 NOTICES OF THE MEETINGS [March 21, 
peror’s autograph, and Sir George Staunton’s Credentials to the 
Court of Japan and Cochin-China [by the Royal Asiatic Society]. 
Bodley’s Revolving and Sliding Window-Sashes [by Mr. Bodley]. 
Specimens of Plumose Alum and Minerals [by the Pharmaceutical 
Society]. 
Enlarged Model of the Lever Scapement [by Mr. Bishop]. 
A Small self-inking Printing Apparatus [from the Bank of England]. 
Talbotypes— Portraits and Views [by Messrs. Henneman and Ma- 
lone}. 
Patent Pearl Glass Pictures [by Mr. Lane]. 
WEEKLY EVENING MEETING, 
Friday, March 21. 
Sir Cuarzes Fettows, V. P. in the Chair. 
Mr. Brockepon, 
On some Properties peculiar to Caoutchouc, and their Applications. 
Caoutcuovuc is a vegetable constituent, the produce of several trees ; 
the most prolific in this substance are, Siphonia Caoutchouc, Urceola 
Elastica, Ficus Elastica, &c. ; of these the Siphonia Caoutchouc extends 
over a vast district in Central America, and the caoutchouc obtained 
from this tree is best adapted for its manufactures. Over more than 
10,000 square miles in Assam the Ficus Elastica is abundant. The Ur- 
ceola Elastica (which produces the Gintawan of the Malays,) abounds 
the islands of the Indian Archipelago. It is described as a creeper in in 
of growth so rapid, that in five years it extends 200 feet, and is from 
20 to 80 inches in girth. This tree can, without being injured, yield 
by tapping, from 50 to 60lbs. of caoutchouc in one season. A 
curious contrast is exhibited in the tardy growth of the tree from 
which the Gutta Percha is obtained. This tree does not come to its 
prime in less than from 80 to 120 years. The produce cannot be 
obtained but by the sacrifice of the tree. It is found in a concrete 
state between the bark and the wood after the tree has been cut 
down, and it is in this condition that, having been scraped out, it is 
sent to our market. 
When coagulated by evaporation or agitation, caoutchouc sepa- 
rates from the aqueous portion of the sap of the trees which yield it. 
This solid and fluid cannot afterwards be reunited, any more than 
butter is capable of mixing with the milk from which it is separated. 
Caoutchouc is a hydro-carbon. This chemical character belongs to 
all varieties of the substance, and many other vegetable constituents, 
though they differ materially in physical qualities. Some specimens 
