CHEMICAL SCIENCE. 211 



steel for trial, which he believed were of a good quality, although he thought 

 there was not any regular manufactory carried on. 



Mr. W. Fairbairn had seen the process in operation two years since in 

 Paris, and the steel that was manufactured by that means Avas of good 

 quality; but the process was carried out only on a small scale, and seemed 

 scarcely suitable for any wholesale manufacture. 



Mr. T. Spencer observed, that a magnetic machine was employed to sepa-_ 

 rate the iron from the earthy matter, when in the state of powder, as found 

 naturally. The pig iron was broken into six or eight inch pieces, and was 

 at first put into the cupola for melting in the ordinary way; but they had 

 now constructed a furnace for the purpose, as the ordinary cupola rather 

 increased the proportion of sulphur in the metal by absorbing some from, 

 the fuel ; the new furnace was a kind of reverberatory furnace, melting the 

 iron in a chamber separate from the fire. The fluid metal was then run into 

 the granulating tank ; and the granules of iron were collected at the bottom 

 of the tank by drawing off the water. 



ON THE HARDNESS OF METALS AND ALLOYS. 



The following paper read before the Philosophical Society of Manchester, 

 England, by Prof. F. Grace Caivert, we obtain from the Journal of the Society 

 of Arts, No. 314. 



The process at present adopted for determining the comparative degree of 

 hardness of bodies, consists in rubbing one body against another, and that 

 which indents or scratches the other is admitted to be the harder of the two 

 bodies experimented upon. Thus, for example : 



Diamond, Quartz, Iron, Tin, 



Topaz, Steel, Copper, Lead. 



This method is not only very unsatisfactory in its results, but it is also in- 

 applicable for determining with precision the various degrees of hardness 

 of the different metals and their alloys. We therefore thought that it would 

 be useful and interesting if we were to adopt a process which would enable 

 us to represent by numbers the comparative degrees of hardness of various 

 metals and their alloys. 



To carry out these views, we devised the following apparatus and method 

 of operating. The machine used is on the principle of a lever, with this im- 

 portant modification, that the piece of metal experimented upon can be 

 relieved from the pressure of the weight employed without removing the 

 weight from the end of the longer arm of the lever. The machine consists 

 of a lever, with a counterpoise and a plate, on which the weights are grad- 

 ually placed ; the fulcrum bears on a square bar of iron, passing through 

 supports. The bar is graduated, and has at its end a conical steel point, 7 

 mm. or 0*275 of an inch long, 5 mm. or 0'197 of an inch wide at the base, and 

 l"2o mm. or 0'049 of a inch wide at the point which bears on the piece of 

 metal to be experimented on, and this is supported on a solid piece of iron. 

 The support, or point of resistance, is lowered or ra'scd by a screw, and 

 when, therefore, this screw is turned, the whole of the weight on the lever is 

 borne by the support and the screw. When it is necessary, by turning the 

 screw, the weight on the lever is reestablished on the bar, and experimented 

 upon. 



