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POPULAR SCIENCE MONTHLY.

thropological investigation by the use of Government aid. A peculiar distinction attaches to this meeting through its reception and entertainment of the French Association, and the subsequent return of the courtesy by the latter body at Boulogne. About three hundred of the French Associationists, among whom were many ladies, came over, on the Saturday of the meeting, under the lead of their president, M. Brouardel, and accompanied by a number of men of science from Belgium. They were met at the pier by the officers of the British Association, and were escorted to the place of meeting and to the sectional meetings toward which their several tastes directed them. The geological address of Sir Archibald Geikie on Geological Time had been appointed for this day out of courtesy to the French geologists, and in order that they might have an opportunity of hearing one of the great lights of British science. Among the listeners who sat upon the platform were M. Gosselet, president of the French Geological Society; M. Kemna, president of the Belgian Geological Society; and M. Renard, of Ghent. Public evening lectures were delivered on the Centenary of the Electric Current, by Prof. J. A. Fleming, and (in French) on Nervous Vibration, by Prof. Charles Richet. Sir William Turner was appointed president for the Bradford meeting of the association (1900). The visit of the French Association was returned on September 22d, when the president, officers, and about three hundred members went to Boulogne. They were welcomed by the mayor of the city, the prefect of the department, and a representative of the French Government; were feasted by the municipality of Boulogne; were entertained by the members of the French Association; and special commemorative medals were presented by the French Association to the two presidents. The British visitors also witnessed the inauguration of a tablet in memory of Dr. Duchesne, and of a plaque commemorative of Thomas Campbell, the poet, who died in Boulogne.

 

Artificial India Rubber.—A recent issue of the Kew Gardens Bulletin contains an interesting article on Dr. Tilden's artificial production of India rubber. India rubber, or caoutchouc, is chemically a hydrocarbon, but its molecular constitution is unknown. When decomposed by heat it is broken up into simpler hydrocarbons, among which is a substance called isoprene, a volatile liquid boiling at about 36° C. Its molecular formula is C5H8. Dr. Tilden obtained this same substance (isoprene) from oil of turpentine and other terpenes by the action of moderate heat, and then by treating the isoprene with strong acids succeeded, by means of a very slow reaction, in converting a small portion of it into a tough elastic solid, which seems to be identical in properties with true India rubber. This artificial rubber, like the natural, seems to consist of two substances, one of which is more soluble in benzene and carbon bisulphide than the other. It unites with sulphur in the same way as ordinary rubber, forming a tough, elastic compound. In a recent letter Professor Tilden says: "As you may imagine, I have tried everything I can think of as likely to promote this change, but without success. The polymerization proceeds very slowly, occupying, according to my experience, several years, and all attempts to hurry it result in the production not of rubber, but of 'colophene,' a thick, sticky oil quite useless for all purposes to which rubber is applied."

 

Dangers of High Altitudes for Elderly People.—"The public, and sometimes the inexperienced physician—inexperienced not in general therapeutics but in the physiological effects of altitude on a weak heart," says Dr. Findlater Zangger in the Lancet, "make light of a danger they can not understand. But if an altitude of from four thousand to five thousand feet above the sea level puts a certain amount of strain on a normal heart and by a rise of the blood-pressure indirectly also on the small peripheral arteries, must not this action be multiplied in the case of a heart suffering from even an early stage of myocarditis or in the case of arteries with thickened or even calcified walls? It is especially the rapidity of the change from one altitude to another, with differences of from three thousand to four thousand feet, which must be