On the Application of Magnetism, S^c. 253 



might accompany it. These masses would be compared with 

 former accidental productions, and the difference observed : 

 at first they would most likely be returned into the bloomery 

 to increase the general produce, but in time become the sub- 

 ject of a separate experiment. It would on trial be found, that 

 they would melt in the common smithy, and by being blown 

 upon in a manner similar to the refining part of the bloomery 

 operation, pass into the state of malleable iron. This would 

 first suggest the idea of a separate fornace and operation for 

 the refinement of iron. The permanent enlargement of the 

 bloomery furnace would ensue. The ores, by a greater descent 

 and longer contact with the fiiel, would be more thoroughly 

 cemented. * The iron would take up carbon in quantity, fu- 

 sibility proportionally increase, and cast-iron in all its varie- 

 ties, from the white conchoidal fractui'e to the large-grained 

 deep grey, be obtained. 



From this period, the making of iron would divide itself into 

 two branches, — the furnace and forge departments ; and, like 

 other judicious divisions of labour, would give new spirit and 

 enterprise to the art : in time foot-blasts and hand-blasts, or 

 bellows, would be abandoned, and a more effectual moving 

 power found on the banks of the adjacent streams. Water- 

 wheels, giving motion to bellows and hammers, would succeed 

 the crude and infantine efforts of a ruder age : and these in 

 their turn would give way to other improvements, in a riper 

 age, much more powei^ful and strikmg. 



XL VI I. On the Application of Magnetism as a Pleasure of Elec- 

 tricity/. By the Rev. J. Cumming, M.A. F.R.S. M.G.S. 

 Professor of Chemistry in the University of Cambridge.* 



i. H E methods hitherto in use for ascertaining the quantity and 

 intensity of the electricity produced either by friction or by 

 galvanic action, are (independently of the shock on the animal 

 Irame, which obviously affords no definite measure,) derived 

 from its power in decomposing water, or fusing meUillic wires. 

 Wlicn the electricity is either small in quantity, or of low in- 

 tensity, there are considerable dilficulties in the practical appli- 

 cation of either of these methods. 



The fusion of platina wire by the elementary battery of 



Dr.Wollaston, proves that the quantity of electricity developed 



by very minute mctalHc surfaces is considerable; yet, exclu- 



" sively of the diinculty in soldering wires that are barely visible, 



it is almost impossible to ascertain their length with any pre- 



• From the Ciimljiidgc Pliilosopliiciil Transactions for 18:??, Tiirt II. 



cision. 



