1917] FORESTRY. 347 



The rubber indxistry, edited by J. Tokbey and A. S. Mandebs (London: 

 Intemat. Rubber d Allied Trades Ex., Ltd., [1917], pp. 516, pi. 1, figs. 3J,).— 

 This book comprises as a whole the official report of the Fourth International 

 Rubber Congress, held in London in 1914. In addition to the papers dealing 

 with various phases of the rubber industry and the discussions thereon, nu- 

 merous papers and discussions dealing with fibers, cotton, oils, etc., together 

 with the principal papers read at the rubber congress held in New York in 

 1912 and a report of the proceedings of the Fourth International Rubber and 

 Allied Industries Exhibition held in London in 1914, are also given. 



A practical tapping experiment conducted on scientific principles, A. W. K. 

 UE Jong (Tcysmaimia, 2S {1911), No. 1, pp. 30-32). — The results are given of 

 comparative tests of a number of methods of tapping rubber that have been con- 

 ducted for a period of three and one-half years. 



Scientific tapping experiments with Hevea brasiliensis, A. W. K. de Jong 

 (Dept. Landb., Nijv. en Handel [Dutch East Indies], Meded. Agr. Chern. Lab., 

 No. 14 (1916), pp. 26, figs. 14)- — Two sets of experiments are reported. In one 

 set various systems of tapping were compared on the same tree. In the other 

 set the various systems of tapping compared were used on different trees. 



Investigations of the quality of plantation rubber conducted under the 

 Cay Ion rubber research scheme (Bui. Imp. Inst. [80. Kensingtmi], 14 (1916), 

 No. 4, pp. 495-566). — The investigations recorded in the present article were 

 conducted under the auspices of the government of Ceylon in conjunction with 

 some of the principal planting companies of the island and with the Imperial 

 Institute. They deal with the effect upon the mechanical properties of the 

 vulcanized rubber of different methods of coagulation, the addition of various 

 substances to the latex in order to retard coagulation, the form of the rubber, 

 the method of drying, " overworking " freshly coagulated rubber in the washing 

 machine, various methods of smoking, drying sheet rubber under tension, rolling 

 up wet and dry sheet rubber, with and without tension, the conversion of wet 

 and dry crepe rubber into block, and separating the rubber from the latex in 

 successive portions. 



The influence of the rubber content of latex on the inner qualities of the 

 rubber, O. de Vkies (Arch. Rubbercult. Nederland. Indie, 1 (1917), No. 1, pp. 

 25-34). — Several experiments were made to determine what effect the dilution 

 of latex has on the inner qualities of rubber. The tensile strength showed no 

 difference, except in the case of a very diluted latex which gave a lower tensile 

 strength. The viscosity was diminished slightly by dilution and the rate of 

 cure in an appreciable degree. In view of the differences in rate of cure noted, 

 it is held to be desirable to dilute the latex to a standard rubber content in 

 urder to obtain rubber of uniform qualities. 



Influence of the amount of acetic acid on the inner qualities of the rubber, 

 O. DE Vkies (Arch. Rubbercult. Nederland. Indie, 1 (1911), No. 1, pp. 35-41). — 

 As a result of experiments conducted in part by the author and in part by 

 P. Arens and N. L. Swart it was found that for quantities of acetic acid ranging 

 from the minimum to four times as much the tensile strength of the rubber 

 shows no difference. The slope or type of rubber remained the same in all 

 experiments in which the rubber was prepared as crepe, although in one ex- 

 periment with smoked sheet rubber the type was sligthly less when using a 

 double quantity of acetic acid. The viscosity increased slightly with increasing 

 quantities of acetic acid. When four times the minimum quantity of acetic 

 acid was used the rate of cure diminished to the extent of 10 minutes in 135. 



It is concluded in brief that the small variations in amount of acetic acid 

 used in actual practice can not be the cause of lack of uniformity in the rubber. 



