■132 Scientific Intelligence. 



he concludes that they belong to two different hydrates. More- 

 over, Charpy finds that the vapor-pressure curve for a 32 per 

 cent cobaltous chloride solution also consists of two portions, the 

 one belonging to the red solution extending to about 40°, while 

 that of the blue solution begins at about 75°. — C. H., cxiii, 

 699, 794, Nov., 1891. G. f. b. 



7. A method of showing Electrical Waves. — Lecher has 

 studied electric waves by means of a Geissler tube which is 

 slipped along between parallel wires which are connected with 

 condenser plates. At certain points the Geissler tube glows, and 

 at nodal points it remains dark. L. Arons encloses a portion of 

 the parallel wires, employed by Lecher, in a long vacuum tube of 

 about 250 cm with a diameter of 6 0m . When the tube is exhausted 

 to about 10 mm pressure, it is filled with light and dark spaces, 

 which indicate electric waves. These waves are produced when 

 there is a certain relation between the capacity of the condenser 

 and the self induction of the wires. — Ann. der Physilc andChemie, 

 No. 3, 1892, pp. 553-559. j. T. 



8. Permanent Magnetic Field. — W. Hibbert points out the 

 use of a permanent magnetic field for vai'ious magnetic measure- 

 ments, and gives the result of a peculiar arrangement which he 

 has employed and which he recommends for testing purposes. A 

 straight bar magnet is supplied at one end with a hemispherical pole- 

 piece of soft iron, at the other end a soft iron disc is screwed which 

 forms the cover of the hemispherical bowl. A circular air space 

 of y 1 ^ of an inch wide separates the cover of the bowl from its 

 edges. A helix of wire surrounds the straight steel bar magnet in 

 the interior of the bowl. By means of this helix the bar can be 

 magnetized to any strength desired. A little coil of fine wire 

 can be quickly thrust through the air space of T 1 g- of an inch which 

 intervenes between the top of the bowl and its edges, thus cut- 

 ting lines of force in a permanent magnetic field. Mr. Hibbert 

 gives some figures which show the great constancy of this appara- 

 tus. There is practically no evidence of magnetic decay in seven 

 months.— -Phil. Mag., March, 1892, pp. 307-314. J. T. 



9. Dielectric Constant and Conductivity. — From experiments 

 conducted by M. E. Bouty, it appears that the dielectric constant 

 only varies slightly under conditions which change the values of 

 conductivity very greatly; thus water and ice have sensibly the 

 same dielectric constant while the conductivity may vary from 1 

 to 10 6 or 10'. — Comptes Rendus, March 7, 1892. J. t. 



10. Aberration. — In a valuable paper on this subject, Lord 

 Rayleigh reviews the work of experimenters on the subject of the 

 hypothesis of a stationary ether or the reverse and thus speaks of 

 Michelson's experiments to determine whether the ether is carried 

 with the earth in its motion through space. 



" It has recently been pointed out by Lorentz that Michelson 

 has overestimated the effect to be expected according to Fresnel's 

 views. The ray which travels perpendicularly to the earth's 

 motion is not affected thereby, but is retarded to the amount repre- 



