1901.] 



on Metals as Fuel. 



505 



steel tubes, and the operation was shown on as large a scale as 

 safety would permit.] The welding of three miles of electrical 

 tramway rails was successfully effected in Brunswick in May 1900. 



As regards the comparison of the use of aluminium as fuel with 

 the electric arc, M. Camille Matignon,* in a very interesting discourse 

 recently dcdivered in Paris, has instituted a comparison between the 

 Goldschmidt process and electric furnace. Quoting Moissan,f be 

 shows that in reducing titanic acid by carbon in the electric furnace 

 having a " laboratory space " of 800 cubic centimetres, 300 horse- 

 power absolute were employed, producing per second 190,500 calories 

 by burning l - 08 kilograms of aluminium. On the other hand, by 

 burning 3*2 kilograms of ferric oxide during one minute in a crucible 

 of about the same capacity as the laboratory of the electric furnace, 

 the rate of evolution of heat is equivalent to 375 horse-power absolute ; 



Fig. 5. — Casing packed round with moulding sand in readiness 

 for the welding operation. 



the latter process does not, however, work continuously, but could 

 readily be made to do so. It should be pointed out that an impure 

 variety of aluminium can be used, and that if the heat needed to 

 effect a given operation is but moderate, the aluminium may be 

 diluted by the presence of an inert substance. 



The photomicrograph (Fig. 6) is from a little test piece of wrought 

 iron (Fig. 7) which was cnt in two. The carefully faced surfaces 

 were then clamped together, and I united them into an excellent weld, 

 without any previous experience in conducting such an operation. 

 No line of demarcation can be seen, and the crystals pass over the line 

 a b, which I know by measurement to be that of the actual weld. 



The very hot molten iron may be used in a somewhat different 

 way for repairing defective castings. In this case the slag is carefully 



* ' Moniteur Scientifique Quesneville,' 4 S. vol. xiv. part i. pp. 357 et seq. 

 f ' Le Four e'lectrique,' p. 19. 



