474 SCIENTIFIC RECORD FOR 1884. 



finds that if the magnetic field is bounded by air the magnetic dif- 

 ference of pressure in the fluid and in the air may be expressed by a 

 hydrostatic pressure, and thus its diamagnetic constant, less unity, can 

 be measured. Using fields varying in strength from 300 c. g. s. to 

 12,000 c. g. s., the increase in height in some cases was more than 32""" 

 for magnetic fluids and — 0.7""' for diamagnetic ones. [Ber. Ak. Berl., 

 January, 1884 ; Fhil Mag., June, 1884, V, xvii, 447 ; Am. J. Sci., Sep- 

 tember, 1884, III, XXVIII, 223.) 



Yon Helmholtz has applied the ordinary chemical balance to the 

 determination of magnetic, moments. Even when the balance is itself 

 not absolutely free from iron, values can be obtained which are con- 

 stant and accurate to within a quarter of 1 per cent. ; moreover, the 

 most essential advantage of the method is that it is quite free from 

 disturbances due to the incessant changes in the terrestrial magnetism, 

 {Ber. Ak. Berl, April, 1883 ; Phil. Mag., January, 1884, V, xvii, 75.) 



Wleiigel and Henrichsen have examined the magnetism of some com- 

 pounds of the alcohol radicals CnHz^+i, by placing them in long glass 

 vessels suspended bifilarly between the pointed half armatures of a pow- 

 erful electro-magnet, charged by the current from 16 to 18 Bunsen cells. 

 The magnetism developed was measured by a torsion method by means 

 of a mirror and scale. The conclusions are : (1) The introduction of CH2 

 into the molecule produces an increase in themolecular magnetism which 

 is nearly constant and has —1,640 for its mean value; (2) the molecular 

 magnetism of a chemical body is equal to the sum of the partial mag- 

 netisms of the alcohol radical and of the other parts of the compound ; 

 (3) HO, I, S, and Br have the same specific magnetism, the mean value 

 of which is —44.3 ; (4) CI, on the other hand, has a diflerent specific 

 magnetism, about —61, a value nearly the same as that found for the 

 radical of acetic acid, —63 ; (5) the alcohol radicals possess the same 

 specific magnetism as their isomers ; and (6) the magnetism of the alco- 

 hol radicals is made up of the atomic magnetisms of the carbon and 

 hydrogen. {FUl. Mag., July, 1884, V, xviii, 78.) 



Leduc has shown (^7. Phys., II, iii, 133) that when a plate of bismuth 

 is iflaced in a magnetic field at right angles to the lines of force, the 

 equipotential surfaces of a current traversing the plate are deflected 

 from their proper direction. Hence the physical condition of the metal 

 must have experienced some alteration. Hurion has taken advantage 

 of Kerr's observation that a mirror placed between the poles of an elec- 

 tro-magnet rotates the plane of polarization of an incident peri)endicular 

 --ay when the magnet is excited, to test this change in the physical 

 properties of bismuth. By pouring the melted metal on a hot plate of 

 glass he prepared a mirror, which was placed between the poles of a 

 Faraday's electro-magnet. It was found that the bismuth rotated the 

 plane of polarization through 18' in the opposite direction to the cur- 

 rent which excites the magnet, and that its electric resistance is in- 

 creased when it is placed in a magnetic field. {Phil. Mag., OoAohi '', 

 1884, V^, xvm, 389.) 



