610 SUMMARY OF CURRENT RESEARCHES RELATING TO 



knowledge of what may be termed the solid geometry of steel. In^ 

 rolled metals it is necessary to make three micrographs in three planes 

 of section at right angles to one another, and from these the exact form 

 in which any constituent exists in the mass can be determined. 



Fig. 140 shows the appearances presented by grains of manganese 

 sulphide under such conditions. 



Prof. Osmond makes known a simplified method of preparing 

 metallic sections for the Microscope. He takes two pieces of hard wood, 

 12 by 9 by 1 in., planed dead smooth on one side ; then by means of 

 liquid glue two sheets of the London Emery Works Co.'s Atlas cloth, 

 No. 0, are evenly attached to the smooth faces. The glue is allowed to 

 set under strong pressure. Next, by means of a smooth piece of steel, 

 he rubs off from one of the blocks as much as possible of the detachable 

 emery. This block is now No. 2 block ; the other is No. 1. 



The steel section, say | in. thick and ^ in. diameter, is rubbed for 

 one minute on No. 1, the motion being straight, not circular; then, for 

 the same time, and in the same manner, on No. 2. The bright but 

 visibly scratched section is then placed in a glass etching dish 3 by 1 by 

 ^ in., and the steel covered with nitric acid sp. gr. 1 ■ 20. In a few 

 seconds the evolved gases adhering to the section change from pale to 

 deep brown, and effervescence ensues. Then the acid is quickly washed 

 away under the tap, and the piece is for a minute immersed in a second 

 dish containing rectified methylated spirit. When the section has been 

 dried by being pressed several times on a soft folded linen handker- 

 chief, it is ready for examination. The structure will be clearly ex- 

 hibited, the innumerable fine scratches visible before etching having 

 virtually vanished. The micrographs illustrating this abstract were 

 prepared in a few minutes by this process. 



Crystallography of Iron.* — MM. Osmond and Cartaud have con- 

 tinued their investigations on this subject. Their paper includes a 

 historical sketch and a description of their methods. The results, 

 which are highly interesting and are illustrated by a large number of 

 beautiful photomicrographs, will be gathered from the following 

 selections. 



Fig. 141, plate XII., shows some isolated crystals, especially cubes 

 ( X 250, vertical illumination). * 



Fig. 142 is an example of some pyramidal cubes obtained in one of 

 the experiments ( X 400, vertical illumination). They are probably 

 tetrahexahedra. Both the above were obtained by the reduction of 

 ferrous chloride. 



Fig. 143 is an example of a dendritic mass of crystals (x 25, 

 oblique illumination). Three main dendrites start from the same centre, 

 forming angles of 120°, while their lateral branches form angles of 

 60° with the dendrites' axis. A. fourth dendrite, projecting laterally, 

 rests upon the plane of the three others, and could not be focussed ; it 

 is indicated by a cloudy appearance. 



Structure of Phosphoretic Pig Metals.f — J. E. Stead points out that 

 ordinary etching fails to distinguish between carbides and phosphides 



* Metallographist, 1900, pp. 275-90; and 1901, pp. 119-49, 236-52 (84 figs.), 

 t Tom. cit., pp. 261-6 (7 figs.). 



