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1. Information from various sources on the increase in adhesive strength between iron surfaces and ebonite brought about by the inclusion of iron oxide in the ebonite was confirmed. 2. In all tests the best results were obtained with ebonite samples No. 1 and No. 2 with addition of 8.2 per cent of red iron oxide (20 per cent based on rubber). 3. Inclusion of 8.2 per cent of red iron oxide in the cement increased the adhesive strength between an iron plate and ebonite 260 per cent measured by the rupture under direct tension as shown in Fig. 1, and 233 per cent measured by the method shown in Fig. 2. These results were confirmed in factory production. A new formula for ebonite cement containing red iron oxide was developed, which considerably increased the adhesive power. In conclusion it should be stated that previous to the laboratory experiment, red iron oxide was used for one year in ebonite formulas for magneto parts. As is well known, most of the parts of a magneto consist of ebonite and cadmium-coated copper armature. However, it has been considered hitherto that red iron oxide acts only as a coloring agent. Red iron oxide is evidently a valuable ingredient for securing strong adhesion between ebonite and metal. Since the Kautchuk factory has adopted the use of red iron oxide in the production of ebonite, the percentage of rejections caused by the separation of armature from ebonite in magnetos had been considerably reduced. This subject requires further experimental confirmation, and the results will be reported in forthcoming publications.