ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 777 



to 800° C, the stress strain relations in steel undergo a change, the 

 " time effect " or " creeping " becoming much greater. A test piece 

 4 in. long, about ' 2 in. diameter, with enlarged ends screwed into steel 

 bars li in. diameter, was heated in a vertical electrical resistance tube 

 furnace. Tension up to 1^ tons per square inch could be rapidly applied. 

 At temperatures of 600°-800° C, the effect of applying the stress was 

 to' produce an immediate extension followed by a slow drawing out. 

 On removal of load an immediate shortening occurred, followed by a 

 slow contraction. Young's modulus was found to decrease considerably 

 with rise of temperature. 



Metallography Applied to Foundry Practice.* — A. Sauveur de- 

 scribes the microscopical outfit adapted for the examination of cast-iron 

 specimens. Vertical illumination is more generally useful than oblique,, 

 which gives a negative image. 



Special Steels. f — L. Guillet summarises the results of his well 

 known investigations on alloy steels. He deals chiefly with ternary 

 steels (containing iron, carbon, and a third element), some quaternary 

 steels being also considered. The author is convinced that vanadium 

 steel, containing less than ' 7 p.c. of that element, is likely to increase 

 largely. Titanium steels and cobalt steels are devoid of any practical 

 interest. While the micrographic character of pearlite steels furnishes 

 only very partial indications of their mechanical properties, it may be 

 at once concluded from the martensitic structure of a steel that it has a 

 high tensile strength and elastic limit. A polyhedral steel has a low 

 elastic limit, high elongation, great resistance to shock, and a hardness 

 depending on the alloy element. Graphite steels are useless for practical 

 purposes, the presence of this constituent causing fragility. 



Induction Galvanometer for the Study of Freezing and Critical 

 Points.J — Dejean describes a modified Desprez-d'Arsonval galvano- 

 meter, in which the moving frame carries two distinct coils. One of 

 these is connected to a thermo-electric couple inserted in the specimen 

 under observation. Variations of temperature cause rotation of the 

 two coils, thus inducing in the second coil a current which is measured 

 by another sensitive galvanometer. The induced current is proportional 

 to the velocity of rotation of the coils, and therefore depends upon the 

 rate of heating or cooling of the specimen. A method of automatic 

 reoording is described, and critical point curves of a number of samples 

 of steel are o-iven. 



e>* 



The Crystallisation of Iron and Steel.§ — In this introduction to 

 the study of metallography, a course of six lectures by J. W. Mellor, the 

 subject is dealt with in an elementary manner, controversial matter 

 being touched upon very briefly. Starting with the general phenomena 

 of crystallisation, allotropy, and entexia, the author considers the modes 

 of solidification and subsequent cooling of solutions, taking particular 

 instances of alloys as examples. The formation of the various constitu- 

 ents of iron-carbon alloys by the cooling, slow or rapid, of a homogeneous 



* Iron and Steel Mag., x. (1905) pp. 309-13. 



t Tom. cit., pp. 314-21 (3 tigs.). J Rev. Met., ii. (1905) pp. 701-4 (4 figs.). 



§ London: Longmans, Green, and Co., 1905, x. and 144 pp.. 65 figs. 



