812 REPORT— 1888 



between the iron former and the furnace-walls. The space inside the box is filled 

 with the furnace charge, which, when ferro-aluminium is to be produced, consists 

 of a mixture of charcoal, bauxite, and iron-turnings, but when the cupro-aluminium 

 is required aranulated copper is substituted for the iron turnings. 



When the furnace limn^: and contents are brought up to the proper leTel, the 

 iron former is carefully lifted, much as a moulder draws a pattern from the 

 sand ; the cover is then luted on to the furnace, and it is ready for the electric 

 ■current. 



This at first is kept down to 3,000 amperes, but as soon as the charge is 

 thoroughly warmed through, and the furnace contents become incandescent 

 througliout, the current is increased to 5,000 amperes, and in about one hour's time 

 the reduction is complete. 



The reduced aluminium trickles through the furnace contents, and collects at 

 the bottom below the electrodes, from which in the furnaces last constructed it 

 can be tapped out continuously. Mr. Cowles believes that the temperature of the 

 centre of the furnace is so high that both the reduced aluminium and the metal 

 with which it is to be alloyed are vapourised and combine as a chemical compound 

 when in this condition, being condensed in the upper and cooler part of the fur- 

 nace, and thence passing down the sides to the bottom. 



The working of the furnace when cupro-aluminium is to be produced leaves 

 nothing to be desired ; the current can be steadily increased from the com- 

 mencement, and towards the end of the reduction it is extremely constant, 

 so that the load on the boilei's, engine, and dynamo is fairly steady throughout ; 

 but when making ferro-aluminium the conductivity of the furnace contents varies 

 through very wide limits, and this brings heavy strains on both the steam-engine 

 and dynamo, which must be met by correspondingly increased strength of parts. 

 The chief feature of the process which strikes a visitor to Milton Works is the 

 small number of men necessary to work the process : two men in the engine and 

 dynamo room, one man at the boilers, and one boy to manipulate the electrodes of 

 the furnaces, are all that are required for the active part of the operation ; two 

 labourers can easily charge and re-line the furnaces, and the remaining staff 

 required for melting down, standardising, and casting into ingots the various 

 classes of furnace products is correspondingly small. 



From the experience already gained, the author sees no difficulty in designing 

 and constructing engines and dynamos to .supply currents of 15,000 or even 20,000 

 amperes, if such be required, for Cowles' furnaces of enlarged size. The electrical 

 difficulties met with in the construction of this large machine have been compara- 

 tively small, whereas the mechanical strains have been unexpectedly great, and 

 must be provided for by extreme solidity and massive construction. 



Recent investigations made in America by Mr. AV. J. Keep have shown that 

 the use of ferro-aluminium is likely to be enormously extended when its properties 

 in relation to cast-iron are thoroughly understood and appreciated by the engmeer- 

 ing world. Mr. Keep is a gentleman who is well known in America, and his 

 statements are entitled to be received with the utmost respect. "VVe already knew 

 in this country that the addition of ferro-aluminium to cast-steel or to ingot iron 

 in such proportion that the finished casting will contain not more than one- 

 thousandth part of aluminium produced extraordinary eflects, in some cases re- 

 ducing the melting-point 300° Cent., and in all cases imparting great fluidity to the 

 metal, thus giving us sharp castings free from blow-holes; but it has remained for 

 Mr. Keep to show us that the addition of an infiuitesimally small percentage of 

 aluminium to cast-iron insures perfect castings, freedom from blow-boles, and 

 almost all the ills to which the ironfounder is subject. Mr. Keep's report is so 

 very full that it is impossible to give any resume of it here. I only call attention 

 to it to show the extreme importance that ferro-aluminium is likely to assume in 

 future engineering, and that as far as we know at present the perfected Cowles' 

 furnace is capable of producing the desired material in any quantity and at a 

 jnoderate cost. 



