354 



SCIENCE, 



Vol. V., No. 117. 



progress could be compared to that of a great 

 atmospheric wave, the pressure being more 

 steady and persistent on the one side (in this 

 case the west) than on the other. Prof. H. 

 A. Rowland exhibited a tabular view of the 

 different values which had been given to the 

 ohm, and criticised that which had received 

 the sanction of the Paris electrical conference 

 as an average derived by giving equal weight 

 to values obtained by admittedly unequal 

 methods. By adding to the table of the Paris 

 conference the results reached hy the American 

 committee in its investigations, and allowing 

 each result its proper proportional value, he 

 had obtained a column of mercury of one 

 square millimetre section and 106.2 centime- 

 tres high as a satisfactory average, which the 

 American committee therefore recommends. 



Perhaps the greatest public interest attached 

 to the two papers of Dr. Graham Bell, given on 

 the last day of the session, one on the possi- 

 bility, while at sea in a fog, of detecting by 

 means of echoes the proximit}- of dangerous 

 objects. Mr. Delia Torre and Mr. Bell had 

 experimented b} r means of a gun and a receiv- 

 ing-trumpet, and had obtained echoes from 

 passing vessels at a distance of from a quarter 

 of a mile to a mile, according to their size. 

 The other showed the results of some experi- 

 ments he had made on the audition of school- 

 children of Washington. He exhibited an 

 audiometer he had devised, in which two flat 

 coils of insulated wire were so adjusted as to 

 admit of separation on a graduated scale meas- 

 uring the distance between their centres. An 

 electrical current, produced by the rotation of 

 a Siemens armature between the poles of a 

 permanent magnet, is passed through one of 

 the coils, and is rapidly interrupted b} r the rota- 

 tion of a disk, a telephone being attached to 

 the other. The intensit}* of the sound pro- 

 duced being dependent upon the intensity of 

 the current induced in the coil to which the 

 telephone is attached, and this upon the dis- 

 tance between the coils, a ready measurement 

 of audition is obtained. The use of this instru- 

 ment proved that ten per cent of the more 

 than seven hundred pupils examined with the 



assistance of Mr. H. G. Rogers were hard of 

 hearing (in their best ear), and seven per 

 cent had very acute powers ; the general 

 range of audition being measured on the 

 scale by the separation of the disks to a 

 distance of from fifty to eighty centimetres, 

 while the total range was from twenty to 

 ninety centimetres. It is known, on the 

 other hand, that in some institutions for the 

 deaf as many as fifteen per cent are merely 

 hard of hearing. 



Dr. Ira Remsen brought to the notice of the 

 academy a case in which chemical action was 

 affected by magnetic influence. Placing a test- 

 tube containing nitric acid in the middle of a 

 coil through which a current was made to pass, 

 he found that the action of the acid on a strip 

 of iron placed in it was sensibly lessened, 

 by at least ten per cent, when compared with 

 that of another strip of iron placed in similar 

 circumstances excepting for the absence of the 

 electric current. Dr. S terry Hunt proposed 

 a classification of the natural silicates which 

 make up a large part of our earth's crust, di- 

 viding them into three groups, according to 

 their bases, and distinguishing them as proto- 

 silicates, persilicates, and protopersilicates. 

 These divisions he believed were more natural 

 than those which divided them according to 

 their sensible qualities, or otherwise, and indi- 

 cated genetic distinctions. 



On the biological side, the papers, while 

 perhaps not so attractive to the public as those 

 already mentioned, were of more than usual' 

 philosophic interest. Prof. E. D. Cope, in a 

 communication on the pretertiary vertebrates 

 of Brazil, which were referred to the cretaceous, 

 Jurassic, and upper paleozoic, and which con- 

 tained many interesting tj-pes, pointed out 

 also that a single pliocene fauna extended from 

 south of our borders to Patagonia, and that 

 neither eocene nor miocene beds had been dis- 

 covered in South America. In a more elabo- 

 rate paper on the plrylogeny of the placental 

 mammalia, based largely on discoveries in the 

 western parts of North America, he claimed, 

 that while many details remain to be worked 

 out, and though their didelphiau ancestors had 



