ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 537 



Ferromagnetism.* — P. Weiss discusses some of the consequences of 

 Laugevin's kinetic theory of ferromagnetism. He deduces from this 

 theory that the magnetic investigation of an alloy resolves itself into the 

 determination of the intensity of magnetisation at saturation, as a func- 

 tion of the temperature. The author's apparatus for this determination 

 is described. The test-piece, in the form of an ellipsoid of revolution, is 

 suspended obliquely between the poles of an electromagnet giving a field 

 sufficiently powerful to magnetise the test-piece to saturation, and the 

 moment of the couple acting on the test-piece is measured. For deter- 

 minations at high temperatures the test-piece is suspended within a small 

 electric-resistance tube furnace. It is suggested that a and /3-iron are 

 not two distinct phases, and that the thermal effects on heating and 

 cooling coinciding with the change from a to /?, or /? to a, are caused by 

 a change in specific heat. 



Dimensional Changes produced in Iron and Steel Bars by Mag- 

 netism.f — W. J. Crawford found that the elongation of mild steel 

 tensile test-pieces, maintained in a state of magnetic saturation through- 

 out the test, was less than the elongation of similar test-pieces when 

 unmagnetised. The amount of decrease of elongation caused by mag- 

 netism varied from 3 to 16 p.c. 



Magnetic Alloys of Manganese. $ — F. Heusler and F. Richarz have 

 continued their investigation of the magnetic properties of certain of the 

 manganese-aluminium-copper alloys. Their explanation of the magnetic 

 behaviour of these alloys is based on the independently established data 

 (1) that copper and aluminium form a compound, AlCu 3 ; (2) that man- 

 ganese and copper form a series of mixed crystals with a minimum in 

 melting-point at a manganese-content of about 30 p.c. 



Silicon-calcium AlloysJ— S. Tamaru has attempted the determina- 

 tion of the equilibrium diagram. Silicon and calcium are miscible in all 

 proportions in the molten state. From about 35 p.c. to 100 p.c. silicon, 

 practically pure silicon separates, which at tH)0° C. reacts with the 35 p.c. 

 liquid to form the compound CaSi. 2 . No other compounds were found, 

 but, owing to the great experimental difficulties encountered, their absence 

 has not been definitely established. 



Sulphur-arsenic System. || — W. P. A. Jonker has investigated this 

 system as an example of " heterogeneous equilibrium," since arsenic 

 passes at atmospheric pressure directly from the solid to the gaseous 

 phase. Both the melting-point* and boiling-point curves were deter- 

 mined ; the equilibrium diagram given accordingly includes the gaseous 

 as well as the liquid and solid phases. As 2 S 2 is partially dissociated in 

 both liquid and gaseous states. As 2 S 3 may be distilled without dissocia- 

 tion. No clear indication of the existence of As 2 S 5 was obtained. 



g* Kev. de Metallurgie, vi. (1909) pp. 680-96 (7 figs.). (Paper presented to the 

 International Congress of Applied Chemistrv, London, 1909.) 

 f Nature, lxxx. (1909) p. 339. 



X Zeitschr. Anorg. Chern., lxi. (1909) pp. 265-79 (3 figs.). 

 § Op. cit., lxii. (1909) pp. 81-8 (1 fig.). 

 || Tom. cit., pp. 89-107 (i figs.). 



