356 



NA TURE 



[February ii, 1892 



iron in consequence of the difference in specific gravity of the 

 two. When the furnace is tapped, the iron runs off to the pig- 

 bed to be cast into the well-known form. The slag is usually run 

 into boxes, which are mounted on wheels. The passion for big- 

 ness which in the present day characterizes nearly all engineering 

 operations of this nature, has extended to slag handling, so that 

 a box will sometimes hold as much as four tons of slag. When 

 the mass is sufificiently cool to stand alone the sides of the 

 mould are lifted ofif by a crane, and the bogie is drawn away to 

 the "tip," or " slag mountain," by a locomotive. As the 

 land covered by the "tip" is often very valuable, in some 

 localities being worth as much as ;^iooo per acre, it is desirable 

 for this reason alone that the slag should be dealt with in some 

 other way. When the iron- works have a sea outlet, the slag is 

 often taken away in vessels constructed for the purpose, and 

 dropped in deep water. The difficulty here is that the big 

 lumps, or "slag-balls," are difficult to handle. To lower them 

 gently into the barge is too costly, and if they are shot in they 

 are likely to start the rivetting. Hand-breaking was, therefore, 

 had recourse to — a tedious and costly process. In order to 

 overcome this difficulty, an ingenious plan, known as the dry core 

 ystem, has been devised. A hollow iron casting was placed so 

 that the slag would flow round it when run in the mould. This 

 was done so that the slag in cooling would contract round 

 the casting and break up into pieces small enough to be tipped 

 into the barge without injury to the plates and rivetting. Mr. 

 Hawdon has not found this method to be successful ; but it is 

 stated that others have followed the plan with advantage. In 

 America a method known as "slopping" is used, and un- 

 doubtedly with success. The molten slag is run on to a surface, 

 and a large but comparatively thin cake is so obtained. When 

 this layer is sufificiently cool, another is formed above it, and 

 then other layers, so that the whole forms a stratified mass, wiih 

 planes of demarcation between. Such a body is broken up with 

 comparative ease. Sometimes the slag is taken away in the 

 molten state in "boats" which are simply tanks on wheels. 

 It is then poured away, leaving a problem for the engineers, and 

 perhaps the geologists, of future generations to solve. There 

 have been other methods of dealing with slag, but these we 

 have not space to describe. Mr. David Joy, a well-known 

 mechanical engineer, took the matter up about twenty years ago, 

 and spent a year or two upon the problem. Some of the devices 

 he originated were extremely ingenious, but for reasons of a com- 

 mercial nature, his efforts were not continued. There are some 

 uses for furnace slag. It is made into bricks, it is drawn into 

 slag-wool, it is made into cement, and is broken up for ballasting 

 railways, pitching streams, or, when made into concrete, for 

 harbour and breakwater works. In spite of these uses, the great 

 bulk of the 12,000,000 tons produced each year has to be 

 tipped to waste, and the disposal of this useless by-product is no 

 small part of the iron-master's expense in running his works. It 

 is to aid this that the apparatus before referred to has been 

 devised by Mr. Hawdon. It consists mainly of two large 

 pulleys, over which there runs an endless chain or a metal belt. 

 The pulleys are mounted on horizontal shafts, parallel to each 

 other, and placed in the same horizontal plane. The pulleys 

 are driven by a steam-engine, and the chain is made to travel in 

 this way. The latter is composed of solid bar links, joined by 

 pins, and on it is mounted a continuous series of shallow pans 

 or trays. At one end of the apparatus the stream of molten slag 

 is directed into the pans, and, as the chain is moving continuously, 

 each pan carries ofi" a part of the material. The pans overhang, 

 so that the metal will not spill on to the links. Between the 

 two pulleys there is placed a large flat tank filled with water, and 

 this is so arranged that the upper part of the endless travelling 

 chain or belt dips into the water, the sag of the belt being 

 sufficient for the purpose. There are guide rollers, but these are 

 details which may be neglected in our explanation of principles. 

 The slag flows into the trays just before they dip into the water, 

 so that the molten metal is at once rapidly cooled. This has 

 the effect of cracking the pieces so much that when they fall out 

 of the trays — which they naturally do when the belt turns over 

 the further pulley — into the barge or waggon,they are broken into 

 convenient sized fragments. Mr. Hawdon claims that by this 

 system a very large saving is effected in transporting slag, and a 

 material of some commercial value is obtained, the pieces being 

 of suitable size for railway ballast or concrete mixing. From 

 what we hear of the apparatus it appears to do its work well so far. 

 The summer meeting of the Institution will be held this year 

 at Portsmouth, on July 26 and three following days. 

 NO. I 163, VOL. 45] 



THE ELECTRICAL EXHIBITION. 



C\^ Saturday evening last the Lord Mayor and the Lady 

 ^^^ Mayoress, accompanied by Mr. Sheriff Tyler, Mr. Sheriff 

 Foster, Sir John Monckton, and many others, went to the 

 Crystal Palace to inspect the Electrical Exhibition. After their 

 walk round, which lasted about an hour and a half, the visitors 

 were entertained at dinner in the large saloon off the south 

 transept. Among the company were the Attorney-General, 

 Sir Robert Rawlinson, Sir Frederick Abel, F.R.S., Prof. W. E. 

 Ayrton, F.R. S., Major-General Webber, Prof. W. Crookes, 

 F.R.S., Mr. Tesla, Mr. W. H. Preece, F.R.S., Sir James N. 

 Douglass, F.R.S., Major-General Festing, F. K. S., Dr. 

 Hopkinson, F.R.S., Mr. A. Siemens, Prof. Kennedy, Prof. 

 Forbes, Prof. Robinson, Prof. Perry, Prof. Hughes, and Prof. 

 Silvanus Thompson, F.R.S. In the unavoidable absence of the 

 Chairman of the Crystal Palace Company, the Hon. D. J. 

 Monson, the chair was taken by the Deputy-Chairman, Mr. G. T. 

 Rait. After the usual loyal toasts, the Lord Mayor proposed 

 " Success to the Exhibition." In doing so he said there was 

 sufficient evidence to warrant him in predicting that the Exhibition 

 would prove a very great success. He recollected how, ten years 

 ago, the electric light occupied the minds of many people, and how 

 at that time the light had w hat proved to be a very bad start. The 

 light was then undertaken more as a speculation. This checked 

 for a time electrical enterprise, though, in his opinion, it had 

 done no great or permanent harm. He admitted, with some 

 degree of shame, that in the City of London they had been very 

 slow to move in the matter. It was possible that they might 

 have hesitated to commit themselves to some appliance that 

 might have been changed on the morrow. They were, however, 

 in favour of the electric light, and the City had been handed 

 over to the new lighting, which ia a short time would be an 

 accomplished fact. 



Dr. Hopkinson, in giving " Electric Science and Industry," 

 remarked that the reaction between these two had been very 

 intimate. 



Prof. Ayrton, President of the Institute of Electrical 

 Engineers, who responded, said that it was impossible to imagine 

 what progress would be made in electricity in another ten years. 

 At present two conductors were necessary for every electric 

 tramcar (laughter). Ihey had anticipated his joke (renewed 

 laughter). One conductor took the current, while the other 

 took the current coin (laughter). It might be that in ten years 

 street lamps would be no longer necessary, as vacuum tubes 

 would be used for walking-sticks (laughter). The smoke plague 

 and fog would no longer trouble U5, for there would be no coal 

 fires when we could bask in the rays of the electric field, repose 

 in the genial warmth of an equipotential surface, and put our 

 feet on a fender composed of horizontal lines of force (loud 

 laughter). One suggestion he would make — that the electric 

 light might be introduced into that room, for the warmth they 

 had borne during the dinner had been surpassed only by the 

 warmth of their reception by the Directors of the Crystal Palace 

 (laughter). 



Mr. R. E. Crompton, President of the Electrical Section of 

 the London Chamber of Commerce, also responded. 



Mr. E. Clark proposed " The Health of the Honorary Council 

 and Committees of the Exhibition." 



Sir F. Abel, in responding, declared that we were on the 

 threshold of great advances in our knowledge of electricity and 

 its applications. 



Mr. W. H. Preece also responded, and congratulated the 

 promoters of the Exhibition upon the fact that they had brought 

 to bear upon the present position of electrical science a fierce 

 and an impartial criticism. 



Mr. Tesla acknowledged some compliments paid to hiinin the 

 course of the evening. 



Sir James Douglass gave "The Crystal Palace Company," 

 and the Chairman responded. 



UNIVERSITY AND ED UCA TIONAL 

 INTELLIGENCE. 



Cambiudge. — Mr. J. J. Lister, of St. John's College, late 

 Assistant Superintendent of the Museum of Zoology, has been 

 appointed Demonstrator in Animal Morphology, in place of 

 Mr. S. F. Harmer. 



Mr. Alexander Scott, of Trinity College, has been appointed 



