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POPULAR SCIENCE MONTHLY. 



tliropolopical investigation by the use 

 of Government aid. A peculiar distinc- 

 tion attaches to this meeting through 

 its reception and entertainment of tlie 

 French Association, and the subsequent 

 return of the courtesy by the hitter 

 body at Boulogne. About three hun- 

 dred of the French Associationists, 

 among whom vi'ere many ladies, came 

 over, on the Saturday of the meeting, 

 under the lead of their president, M. 

 Brouardel, and accompanied by a num- 

 ber of men of science from Belgium. 

 They were met at the pier by the offi- 

 cers 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 Arcliibald 

 Geikie on Geological Time had been ap- 

 pointed 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 Brit- 

 ish science. Among the listeners who 

 sat upon the platform were M. Gosse- 

 let, president of the French Geological 

 Society; M. Kemna, president of the 

 Belgian Geological Society; and M. Re- 

 nard, of Ghent. Public evening lec- 

 tures were delivered on the Centenary 

 of the Electric Current, by Prof. J. A. 

 Fleming, and (in French) on Nerv'ous 

 Vibration, by Prof. Charles Richet. Sir 

 William Turner was appointed presi- 

 dent for the Bradford meeting of the 

 association (1900). The visit of the 

 French Association was returned on 

 September 22d, when the president, ofii- 

 cers, and about three hundred members 

 went to Boulogne. They were wel- 

 comed by the mayor of the city, the 

 prefect of the department, and a repre- 

 sentative 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 Bou- 

 logne. 



Artificial India Rubber. — A recent 

 issue of the Kew Gardens Bulletin con- 

 tains an interesting article on Dr. Til- 



den's artificial production of India rub- 

 ber. India rubber, or caoutchouc, is 

 chemically a hydrocarbon, but its mo- 

 lecular 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 mo- 

 lecular formula is Collg. Dr. Tilden ob- 

 tained this same substance (isoprene) 

 from oil of turpentine and other ter- 

 penes 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 everj'thing I can think of as 

 likely to promote this change, but with- 

 out success. The polymerization pro- 

 ceeds very slowly, occupying, according 

 to my experience, several years, and all 

 attempts to hurry it result in the pro- 

 duction not of rubber, but of ' colo- 

 phene,' a thick, sticky oil quite useless 

 for all purposes to which rubber is ap- 

 plied." 



Dangers of High Altitudes for 

 Elderly People. — " The public, and 

 sometimes the inexperienced physician — 

 inexperienced not in general therapeu- 

 tics 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 under- 

 stand. 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 throe thousand 

 to four thousand feet, which must be 



