CAOUTCHOUC, OR INDIA RUBBER. 



53 



into Dundee in 1838 was only 1,136 tons, it may now be estimated at 

 40,000 tons. With respect to the future supply of jute, we are able to 

 state, on the authority of Dr J. Forbes Watson, that the growth of India 

 is at least 300,000 tons, of which upwards of 100,000 tons are exported as 

 gunny-bags, besides 40,000 tons in the raw state : it appears also that the 

 better qualities are mostly retained for home use, and that the production 

 admits of unlimited extension. We assume that, except in cases of natural 

 monopoly, great demand is an essential condition of abundance and cheap- 

 ness, and we therefore look upon the increasing wants of our manufacturers 

 as the certain cause of a vast increase in the growth and importation of 

 this useful commodity. 



The following shows the comparative shipments of jute from Calcutta 

 in the last three seasons (October to June inclusive) in bales : — 



1858-59. 



1S59-60. 



1860-61. 



To Great Britain 

 France - - 

 America - - 



Total - 



356,479 



29,568 

 15,768 



401,815 



235,138 

 19,429 

 13,694 



268,261 



283,775 

 28,440 

 20,441 



332,656 



The present London wholesale prices (14th August, 1861) range from 

 121. per ton for very ordinary, to 21^. for fine. 



CAOUTCHOUC, OE INDIA RUBBER. 



BY BENJAMIN NICKELLS. 

 II.* 



Caoutchouc, in its chemical relationship to the hydrocarbon series, 

 possesses many features of interest which claim the notice of men of 

 science; yet little beyond "ultimate analysis," and examination of its 

 physical characters, has been done towards furthering additional research. 



Natural or native caoutchouc, as stated in a previous paper, exists in 

 the form of a fluid emidsion obtained from numerous tropical plants. In 

 examining this sap or juice, specimens of which are now common in this 

 country, we find it to eonsist of a milky fluid, having the consistency of 

 cream, and varying in colour from pure white, down to several shades of 

 yellow. To preserve this fluid emulsion intact as collected from the plant, 

 it should be sealed up in vessels carefully excluded from atmospheric 

 influence ; otherwise it speedily becomes covered with a pellicle of solid 

 matter, which gradually increases in thickness until the whole of the caout- 

 chouc has become separated. 



The action of heat, as well as that of acids, causes rapid coagulation and 



* See Technologist for July 1861 (vol. i., p. 382). 



