238 Scientific Intelligence. 
dant. Leo Arons has applied to this problem, with certain 
modifications, Cohn’s method for the measurement of polarization 
in fluids (Wied. Ann., xiii, 665, 1881), which in general terms is 
as follows :—One branch of a Wheatstone’s bridge contains the 
polarizing element and the liquid. In place of the latter a metal- 
lic resistance can be interposed. The bridge contains a galva- 
nometer and one coil of a dynamometer, while the other with the 
secondary coil of an induction apparatus forms the second diago- 
nal of the parallelogram. ‘The resistance together with the inter- 
posed liquid are so arranged that the dynamometer gives no 
indication when the induction coil is excited. At the same time 
the deflection of the galvanometer is read. Then the liquid is 
replaced by a metallic resistance until the dynamometer again 
gives no indication, and the galvanometer is again read. These 
observations can be applied toa simple expression which gives the 
contrary electromotive force of the liquid. Instead of the liquid 
the voltaic are can be substituted. In preliminary trials, Arons, 
obtains with a current strength of 34 amperes, a contrary 
electromotive force, in the electric lamp employed, of 40°6 volts, 
together with an arc resistance of 2:1 ohms. With 4:1 amperes; 
the contrary electromotive force was 39°6 volts, and resistance 1°6 
ohms. Arons is apparently unacquainted with the investiga- 
tions of Professor Cross of the Massachusetts Institute of Tech- 
nology upon this subject.—Ann. der Lede und Chemie, No. 1, 
1887, p. 95-99. Bie at 
4, Generalization of the Wheatstone Bridge.—O. FROw.LIcH 
investigates the conditions of equilibrinm when sources of electro- 
motive forces are interposed in one of the branches of the bridge 
or in one of its diagonals, and shows that Mance’s method is only 
a special case of a more general law; and that the statement in 
Maxwell’s Electricity and Magnetism, vol. i, p. 411, that Mance’s 
method is the only one in which the current of the cell remains 
unchanged, is not correct.—Ann. der Physik und Chemie, No. 1, 
1887, pp. 156-161. Bie is, 8 
5. Onanearly perfect simple pendulum.—My. J.'T. BoTToMuey, 
ou the University of Glasgow, suspends a small shot ‘of about 
zg of an inch in diameter, by a single silk fibre (half a cocoon 
fibre) two feet long, in a elass tube three quarters of an inch in 
internal diameter and exhausts the latter to about one tenth of a 
millionth of an atmosphere. Starting with a vibrational range of 
4 inch on each side of its middle portion, the vibrations can be 
easily counted after the lapse of 14 hours.—Phil. Mag., Jan., 
1887, p. 72. BB 
6. Acoustical Investigations—F. MrtpE continues his com- 
munications upon his acoustical experiments, with an account 
of the vibrations of bell-shaped vessels, together with the move- 
ments of fluids which they may contain. Ingenious methods of 
studying the movements of the fluids are given, together with the 
figures obtained. In certain cases a thin layer of petroleum 
covers the surface of the water, which fills the vessel; in other 
