MECHANICS AND USEFUL ARTS. 21 



extra quantity of fettlins:, which reduced the benefit of his o^ood 

 yield of iron. But to obviate this he adopted water-bridges. They 

 absorb much heat from the furnace, — this gentleman states equal 

 to 8 or 10 pounds of coals per heat. We think this a low estimate, 

 as the getting up has to be taken into account. However, it is 

 obvious that, by the arrangement described above, the heat ab- 

 stracted by the circulating current of air is restored to the furnace. 

 This forms an important feature in the improvement. The fuel is 

 fed at the highest point of the furnace by a slide door on the stand- 

 ing, and there are proper arrangements for shoring up, when re- 

 quired, also on the standing. A current or currents of air are also 

 forced in below into a closed chamber, by which the cinders are 

 most completely burnt up. The-steam being decomposed, passing 

 through the incandescent fuel, transfers the intense heat into the 

 working chamber. The quantity of refu^ produced is very small. 

 The clinkers are readily removed with a light hook, and the men 

 are never occupied more than a few minutes in the operation, 

 generally one minute. Thus we are justified in saying this is 

 perfect combustion ; it ajDpears to us there is no room for further 

 improvement. But to restore the waste heat into the generator, 

 furnaces are now being put up by Messrs. Hannah & Sons, where 

 pretty nearly all the heat will be regenerated. These furnaces 

 can go to any intensity, and the flame is under perfect control to 

 oxidize or not ; or the iron may be drenched with intensely hot 

 air. The cost of alteration to existing furnaces is very small ; 

 when erecting new ones about the same price. The advantages 

 obtained are no smoke, no cinders, a large yield of iron, and bet- 

 ter in quality. If we assume 25 cwt. of coals used as the Cleve- 

 land average for puddling, it appears to be about 8 cwt. to the ton 

 saved. Much fettling is saved, there are less repairs, and no 

 grate bars to replace. We think there is sufficient inducement to 

 ask its adoption." 



MANUFACTURING STEEL BY THE USE OF NITRATE OF SODA. 



Several attempts have been made to use nitrates in converting 

 iron into steel by placing the substances below the level of the 

 bath of molten metal, and thereby causing the oxygen of the other 

 gases evolved by the decomposition under heat to pass up through 

 the metal. Experience, however, showed that the reactions took 

 place so rapidly and with such force as to throw about the metal. 

 But Mr. Hargreaves has fully comprehended the necessity for 

 finding a remedy for the too rapid decomposition of the salts. The 

 salt taken by Mr. Hargreaves is the nitrate of soda, on account of 

 its cheapness and high percentage of oxygen. The most impor- 

 tant function of the nitrate of soda would not, however, so much 

 consist in its decarbonizing powers, as in its being an agent " in 

 removing the metalloids, silicium, sulphur, and phosphorus, and 

 the semi-metal, arsenic, by forming with them compounds of so- 

 dium;" the materials are placed below the fused cast iron, and 

 the products of the decomposition rise up through the fused metal. 



