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Stereophotographic Surveying
Sept., 1913.]
CURRENT TOPICS.
345
whilst in another table the specific gravity, flash point, calorific value, and actual evaporative power of various kinds of liquid fuel are given; heavy tar oil is shown to be considerably inferior to a good petroleum fuel oil as a fuel. It is stated that air carburetted with petrol vapor gives good results in the Bone and McCourt system of flameless surface combustion, and experiments have also indicated that fuel oil, finely atomized with air in the correct proportion, and then blown into the tubes containing the granular material, will also prove efficient if the granular material be previously heated. Stereophotographic Surveying. O. LEMBERGER. (Eng. News, lxix, 6o2).--A short history of the development of photographic surveying in Europe, with some examples of photographic location of certain railways, such as the Jungfrau Railway, and examples of topographical surveys. The theory of photogrammetry is briefly explained, and also the theory and practice of stereophotogrammetry. The instruments used for stereophotogrammetry, the stereomicrometer and the stereocomparator, are described, with diagrams of their construction and examples of their practical application. Finally, an instrument called the stereo-autograph is described, which automatically draws a map while an operator manipulates the stereocomparator. Contour lines may be drawn automatically on a map or on a photographic print. Illustrations are given of the use of the instrument for a survey of the 'Ostler Mountains in the Tyrol. Other possible uses are suggested. Vulcanization of Rubber. G. BERNSTEIN. (Z. Che~. Ind. Kol., xii, 193, 273.)--Expcriments with different kinds of rubber showed that the viscosity is diminished by heating, by mechanical working, and by exposure to ultra-violet rays, and that if the depolymerization indicated by this reduced viscosity bc carried to completion, the final result is the same, whatever the agency employed --i.e., solutions of the dcpolymcrized rubber of the same concentration show the same constant viscosity. With Frank and Marckwald's viscosimeter, and using a 3 per cent. solution of rubber in xylene, the final constant viscosity value is 15 seconds. Depolymerization on heating takes place most rapidly between 60 ° and 85 ° C., according to the kind of rubber, and these temperature limits are close to the temperature above which, according to Spencc, vulcanization occurs most actively. The vulcanization of rubber can be produced by exposing a xylcne solution of rubber and sulphur to ultra-violet rays. A xylene solution of a mixture of Hevea plantation rubber with 6 per cent. of sulphur was allowed to evaporate so as to leave a thin film on a transparent quartz plate. This was covered by another quartz plate and exposed on both sides for 4o minutes, at a distance of 15 cm. to the rays from a Herams lamp of 3 amperes and IiO volts. The film then possessed
CURRENT TOPICS.
345
whilst in another table the specific gravity, flash point, calorific value, and actual evaporative power of various kinds of liquid fuel are given; heavy tar oil is shown to be considerably inferior to a good petroleum fuel oil as a fuel. It is stated that air carburetted with petrol vapor gives good results in the Bone and McCourt system of flameless surface combustion, and experiments have also indicated that fuel oil, finely atomized with air in the correct proportion, and then blown into the tubes containing the granular material, will also prove efficient if the granular material be previously heated. Stereophotographic Surveying. O. LEMBERGER. (Eng. News, lxix, 6o2).--A short history of the development of photographic surveying in Europe, with some examples of photographic location of certain railways, such as the Jungfrau Railway, and examples of topographical surveys. The theory of photogrammetry is briefly explained, and also the theory and practice of stereophotogrammetry. The instruments used for stereophotogrammetry, the stereomicrometer and the stereocomparator, are described, with diagrams of their construction and examples of their practical application. Finally, an instrument called the stereo-autograph is described, which automatically draws a map while an operator manipulates the stereocomparator. Contour lines may be drawn automatically on a map or on a photographic print. Illustrations are given of the use of the instrument for a survey of the 'Ostler Mountains in the Tyrol. Other possible uses are suggested. Vulcanization of Rubber. G. BERNSTEIN. (Z. Che~. Ind. Kol., xii, 193, 273.)--Expcriments with different kinds of rubber showed that the viscosity is diminished by heating, by mechanical working, and by exposure to ultra-violet rays, and that if the depolymerization indicated by this reduced viscosity bc carried to completion, the final result is the same, whatever the agency employed --i.e., solutions of the dcpolymcrized rubber of the same concentration show the same constant viscosity. With Frank and Marckwald's viscosimeter, and using a 3 per cent. solution of rubber in xylene, the final constant viscosity value is 15 seconds. Depolymerization on heating takes place most rapidly between 60 ° and 85 ° C., according to the kind of rubber, and these temperature limits are close to the temperature above which, according to Spencc, vulcanization occurs most actively. The vulcanization of rubber can be produced by exposing a xylcne solution of rubber and sulphur to ultra-violet rays. A xylene solution of a mixture of Hevea plantation rubber with 6 per cent. of sulphur was allowed to evaporate so as to leave a thin film on a transparent quartz plate. This was covered by another quartz plate and exposed on both sides for 4o minutes, at a distance of 15 cm. to the rays from a Herams lamp of 3 amperes and IiO volts. The film then possessed