The set-up which was used to raise and drop the stirrer by means of this flasher button is indicated in Figure 2. In this figure, A is a socket containing the flasher button; BI and BIare light bulbs which reduce the current to the proper value. C is a relay which makes and breaks the current through the solenoid. D is a condenser which prevents sparking across the relay. E is a solenoid. F is a rod of iron sealed inside of a glass tube to protect i t from the reaction mixture. G is a platinum stirrer sealed to the piece of tubing which contains F. The degree of stirring may he regulated by varying the current through the solenoid. Artificial Analog of Rubber. The investigation of the problem of the chemistry of rubber by Staudinger and his schwl has been complicated in the past, on the natural side by the very great susceptibility of caoutchouc t o oxidation, and on the synthetic side by the f a d that the synthetic caoutchouc produced by condensation of the hydrocarbon isoorene mav have a very different structure from the natural material. owinr to the possibility of molecules uniting together into complex three-dimensional systems. A new a~oroach t o the subject is described by Prof. Staudin~e-er in the Tanuarv Berichle .. (vol. 62, pp. 241-263). Instead of isoprene, the aromatic compound styrene is condensed. This, being a benzene derivative, cannot furnish a true caoutchouc, hut the condensed product which it gives, polystyrene, may he regarded as a "model" of the natural substance, and can he accurately investigated since its constituent groups can link together only in one single chain. An interesting discovery is that if the condensation is carried out a t high tel?peratures, for example, 240°C., the product is relatively simple, being composed of some thirty units, whereas if the styrene is eondeused slowly a t ordinary temperatures it yields a very complex, colloidal substance, composed of some hundred thousand units, and resembling natural caoutchouc. All intermediate degrees of complexity are obtainable by varying the temperature and the time of condensation, and a t any temperature the product obtained is a complex mirture of numerous members of a series, comparable with the series of natural paraffins; the most highly condensed products, and these only, resemble caoutchouc in viscosity. and in elastic swelling pr&erties. Professor Staudinger concludes that natural caoutchouc is built up on a similar plan of polystrene, and that it contains long chains of some thousand molecules of the unit "polyprene" (CsHa).-Nature (London), 123, 472 (Mch. 23, 1929). Einstein's Fiftieth Birthday. The fiftieth birthday of Prof. A. Einstein occurred on March 14th, and brought congratulations from all parts of the world. The German Chancellor bailed him as "Germany's great savant," and the Berlin municipality gave him the life tenancy of a pleasantly situated mansion. The University of Paris conferred an honorary degree. The Zionists are t o plant an "Einstein W o o d near Jerusalem. ,Never before has the name of a scientific worker meant so much to the average man. Yet the creator of relativity and of the unitary field theory remains a quiet and retiring personalitywho dislikes publicity and society. His appearance suggests a musician, and indeed his love of music is one of his leading characteristics. Last year he gave a violin recital for a charity. He finds much pleasure in Russian literature, and appreciates modern ideas in architecture. He is an ardent sympathizer ,with efforts for world peace. Recently his health has noi b;e'eh good, hut he says, "Illness has its advantage: one learns to think. I have only just begun to think."Nature (London),123,464 (Mch. 23, 1929).
