TRANSACTIONS OF THE SECTIONS, 105 



received a communication from Mr. Davics Gilbert, in which he stated 

 that there was a district in Cornwall where the soil contained a large 

 proportion of arsenic ; and that no plants could grow in it except some 

 of the Leguminosse. By analysis, this soil yielded him about fifty per 

 cent, of arsenic, in the form of a sulphuret ; the rest being composed 

 principally of sulphuret of iron and a little silica. He had already as- 

 certained that a little of the sulphuret mixed in soils produced no inju- 

 rious effect on Sinapis alba, barley, or beans ; and that they flowered 

 and seeded freely when grown in it. Although the want of solubility 

 in the sulphuret might be assigned as a reason for its inactivity, yet it 

 was certainly taken up by water in small quantities, and imbibed by the 

 roots of plants. Upon watering them with a solution of arsenious acid 

 he had found that they would bear it in larger proportions than was 

 presupposed. 



On Caoutchouc. By Professor Roylb. 



Professor Royle stated that he had been induced to draw up the sub- 

 stance of the present communication in consequence of a conversation 

 which he had lately held with the director of an extensive establish- 

 ment for the manufacture of this substance into various articles of com- 

 merce, from whom he learned that the demand at present exceeded the 

 supply. Professor Royle asserted that, in the East, there might be any 

 quantity of the article procured from a great variety of plants, if the 

 natives could only be induced to collect it with sufficient care. The 

 South American caoutchouc is generally collected with so much greater 

 care than that from the East Indies that it bears a very much higher 

 price in the market. That from the latter country is of excellent qua- 

 lity, but generally much mixed with a considerable quantity of dirt, 

 bark of the tree, and other extraneous matter. Professor Royle then 

 enumerated several of the uses to which caoutchouc is now applied, and 

 stated that the East Indian kind, from its great impurity, can only be 

 used for the purposes of distilling from it the volatile spirit caoutchou- 

 cine. At the present time, the article from the East is selling at 2d. 

 per pound, whilst that from Para fetches from 2s. 6d. to 3*. per pound. 

 It is very remarkable that a substance so incorruptible in water, and so 

 insensible to a variety of chemical re-agents, should have remained so 

 long unknown in Europe. Professor Royle then recapitulated the chief 

 circumstances of its early commercial history, and the method employed 

 for procuring and preparing it. The substance is probably also pro- 

 duced in the southern parts of China, and is now exported from the 

 island of Singapore. The Mauritius, Madagascar, Java, Penang, were 

 then instanced as other localities from whence caoutchouc was obtained, 

 and reference was made to the manner in which it was prepared in the 

 latter country. By experimenting upon other species of the same fami- 

 lies as those which were known to contain caoutchouc, it would pro- 

 bably be found that the list of plants from which it could be obtained 

 might soon be much increased. Professor Royle then mentioned 

 those families in which it had already been observed to exist in greater 



