

- 343 



to be the production of polymerised terpenes having some of the 

 elastic properties of rubber. 



A more promising, because a more scientific way, is that out- 

 lined in Heinemann's patent N. 21 772 of 1907. Here a true syn- 

 thesis is attempted. It is based upon the well known fact that 

 rubber is probably a polymer of the semi-terpene isoprene. The 

 first step is the production of the unsaturated hydrocarbon divinyl, 

 CH 2 : CH.CH : CH 2 . This is obtained by passing mixed acetylene 

 and ethylene gases through a heated tube. With methyl chloride, 

 divinyl yields isoprene (methyl divinyl, CH 2 : C(CH 3 ). CH : CHJ ; 

 and the isoprene on treatment with strong hydrocloric acid is con- 

 verted, by a union of molecules, into a substance closely resembling 

 caoutchouc, if not identical with it. The raw materials, so to speak, 

 are thus acetylene, ethylene, and methyl chloride, which are them 

 selves obtained by any of the ordinary methods, e. g. from calcium 

 carbide, alcohol, and beet sugar residues respectively. " 



XXXI. 



Weeds and Diseases of plants. Noxious weeds and their 

 prevention. Vegetable parasites. Parasitic and sapro- 

 phytic Fungi. Conditions affecting parasitism. - Bacteria 

 and plant diseases. Resistance of plants to disease. 



Law and Custom in regard to Noxions Weeds in English 

 Farming. The Agricultural Legislation of 1909. Journal 

 of the Royal Lancashire Agricultural Society, 1910, p. 62. 



The following is an extract from an article of Mr. T. C. Jackson 

 on the Agricultural Legislation of 1909: 



It may be worth while to consider for a moment the position 

 of the English farmer in regard to noxious weeds. We may con- 

 sider the farmers' position from two points of view, viz: his 



relationship in the matter of weeds to his landlord and secondly 

 to his neighbour. 



As far as his landlord is concerned, a yearly tenant is not 

 esponsible for permissive waste. Thistles and charlock grow na- 



