298 



SCIENCE. 



[Vol. IV., No. 85. 



full of water. After a while the water will acquire 

 the same velocity of rotation as the table, and will 

 come to a state of equilibrium. The outer edge of 

 the water in the canal will then stand a little higher 

 than the inner edge. Let us now apply a little 

 motive force to the water, and by means of a pump 

 cause it to flow in the canal in the same direction in 

 which the table is already rotating: it is evident that 

 it will stand higher on the outer edge, and lower on 

 the inner edge of the canal, than before. But, should 

 we cause it to flow in the opposite direction to the 

 motion of the table, it will stand lower on the outer 

 edge, and higher on the inner edge, than in its posi- 

 tion of equilibrium. 



The experiment made by Mr. Shelford Bidwell 

 may also be illustrated by putting a partition in the 

 canal so as to divide it into two circular concentric 

 troughs, and making a little opening in the partition 

 at some point; then taking two points near the open- 

 ing in the partition, one in one trough and one in 

 the other, if they are very close to the partition, the 

 point in the outer trough will be at a lower level than 

 that in the inner one; but if they are not close to the 

 partition, but one is taken close to the outer edge of 

 the outer trough and the other close to the inner 

 edge of the inner trough, then the point in the 

 outer trough will be at a higher level than that in 

 the inner trough, though the difference in level will 

 be only about half of what it would have been had 

 there been no partition separating the canal into two 

 troughs. Professor Forbes called attention to the 

 fact that the classification of the metals according to 

 their thermo-electric qualities gives not only exactly 

 the same division into positive and negative, but that 

 the very order obtained in that way corresponds to 

 that obtained by classifying according to the Hall 

 effect, except possibly in the case of aluminium. 



Prof. Silvanus P. Thompson read a paper on the 

 government of dynamo-machines. It is a subject of 

 considerable importance from the practical point of 

 view, and Professor Thompson has given a great deal 

 of thought to it. After reviewing and criticising the 

 methods used by Marcel Desprez and Ayrton and 

 Perry, he proposed a method devised by himself, and 

 which he has successfully employed. It was what he 

 calls a dynamometric method, since it is based on the 

 employment of a transmitting dynamometer as a gov- 

 ernor. In this way the governing action is made pro- 

 portional to the rate of work. Professor Thompson's 

 very simple device is to have resistance-coils so placed 

 in the pulley of the transmitting dynamometer, which 

 is fixed to the shaft, that as the rate of work varies, 

 and the movable pulley of the dynamometer changes 

 its position with reference to the fixed pulley, resist- 

 ance will be added to or taken from the circuit; thus 

 modifying the current, and bringing about the re- 

 quired government. 



An interesting paper was also read by Professor 

 Wead, in which he gave the results of some experi- 

 ments made on the energy absorbed by organ-pipes in 

 producing sound. Among other things, he showed 

 that reeds are very much more efficient than pipes, 

 giving far louder sound with less expenditure of 



energy. He also showed that the results of his 

 experiments, on the energy absorbed by pipes of simi- 

 lar shape but different pitch, confirm the practical 

 rule adopted by organ-builders in increasing the pro- 

 portional diameter of the pipes as the pitch increases, 

 so as to maintain equal loudness. Professor Wead 

 finds, that for a rise in pitch of sixteen semitones, 

 one-half the energy is required in order to give a 

 scale of sensibly equal loudness. 



Professor Loudon read a very interesting paper, 

 giving simple geometrical constructions for deter- 

 mining the cardinal points of a thick lens or a system 

 of thick lenses. It is to be hoped that he may pub- 

 lish his paper in full. 



Many other papers were read of more or less in- 

 terest, but those given are the most important. 



NOTES AND NEWS. 



It may be well to call attention once more to the 

 course of eighteen lectures by Sir William Thomson, 

 on molecular dynamics, at the Johns Hopkins univer- 

 sity in October. Professors and students of physics 

 are invited to attend. 



— The following persons were elected officers of the 

 American association for the advancement of science 

 for the ensuing year: President, H. A. Newton of 

 New Haven, Conn. ; permanent secretary, F. W. Put- 

 nam of Cambridge (office, Salem, Mass.); general 

 secretary, Charles Sedgwick Minot of Boston, Mass. ; 

 assistant general secretary, Charles C. Abbott of 

 Trenton, N.J. ; treasurer, William Lilly of Mauch 

 Chunk. Section A, mathematics and astronomy, J. 

 M. Yan Yleck of Middletown, Conn., vice-president; 

 E. W. Hyde of Cincinnati, O., secretary. Section B, 

 physics, C. F. Brackett of Princeton, N.J., vice-pres- 

 ident; A. A. Michelson of Cleveland, O., secretary. 

 Section C, chemistry, W. R. Nichols of Boston, Mass., 

 vice-president; F. P. Dunnington, University of Vir- 

 ginia, Va., secretary. Section D, mechanical science, * 

 J. Burkitt Webb of Ithaca, N. Y., vice-president; 

 C. J. H. Woodbury of Boston, secretary. Section E, 

 geology and geography, Edward Orton of Columbus, 

 O., vice-president; H. Carvill Lewis of Germantown, 

 Penn., secretary. Section F, biology, Burt G. Wilder 

 of Ithaca, N.Y., vice-president; M. C. Fernald of 

 Orono, Me., secretary. Section G, histology and mi- 

 croscopy, S. H. Gage of Ithaca, N.Y., vice-president; 

 W. H. Walmsley of Philadelphia, Penn., secretary. 

 Section H, anthropology, W. H. Dall of Washington, 

 D.C., vice-president; Erminnie A. Smith of Jersey 

 City, N.J., secretary. Section I, economic science 

 and statistics, Edward Atkinson of Boston, Mass., 

 vice-president; J. W. Chickering of Washington, 

 DC, secretary. 



— The next meeting of the British association will 

 be held at Aberdeen. 



— It was suggested by Capt. Bedford Pim, at Phila- 

 delphia, that the 1886 meeting of the American asso- 

 ciation should be held in London. It is understood 

 that there is no constitutional obstacle in the way of 

 the association meeting outside of America; and it 



