Polytechnic Association Proceedings. 677 



the melting point at will. It will surprise even practical iron 

 foiuiders to leuni his experiments proved that the melting point of 

 different samples of charcoal iron, made at his own blast furnaces, 

 varied more than eight hundred degrees F. Charcoal iron gene- 

 rally melts at seven hundred degrees higher temperature than coke 

 iron. The contraction on cooling is greatest in charcoal iron, and 

 in most cases, it has the greatest density when solid. In examining 

 various specimens of casting, M. Schott brought to his aid the 

 microscope, and was thus enabled to detect certain differences which 

 chemical analysis had failed to explain. 



M. Schott avers that all crystals of iron are of double pyramid 

 form, having a variable axis compared with the ^ze of the base. 

 The finer kinds of crystaline iron have pyramids of only half the 

 height of those of the coarsest variety. The best quality of iron 

 has the smallest crystals and pyramids of the broadest base in pro- 

 portion to their height. The pj-ramids of steel are found to vary 

 in the same way, according to the nature and quality of the material. 

 The unifonnity and parallelism of the crystals are important 

 elements in the structure of steel. A field of iuvestisfation haai 

 now been opened by M, Schott, which should induce others to 

 make extensive operations in this direction. The iron ore used by 

 him is not different from that found in many other places. It is 

 reduced in a series of small charcoal furnaces in the vicinity of the 

 mines, which are situated in Northern Germany, near the town of 

 Brunswick. The secret of M. Schott's success in makinjr small and 

 fine castings, lies in the fact that the whole process is the result of 

 a long series of scientific observations. 



Mr. Dudley Blanchard remarked that he had seen some very fine 

 iron castings made by exhausting iu the molds at the time of pour- 

 ing the metal. 



NEW USE FOR PETROLEUM. 



The light products of petroleum are found to be preferable to 

 tui^pentine for cleansing type and wood engravings. 



ELECTROTYPE tMPROVEMENT. 



M, Bouillet, of France, has found that adding a very minute 

 cj[uantity of gelatine to the bath of sulphate of copper effectually 

 prevents the brittleness which has hitherto been an objectionable 

 quality in copper deposited by electrolysis. The manner in which 

 gelatine thus increases the . tenacity of copper, has not been 

 explained, . 



