198 Miscellaneous Intelligence. 



Whether the currents were equal, or unequal ; of one, or of 

 many hundred pairs of plates ; put in action together, or succes- 

 sively ; when three currents were used in place of two j when 

 they were made to intersect each other at acute angles, or to 

 pass parallel to each other j even when they were made to pass 

 through the same metallic communication — still no interference 

 or alteration was observed. 



M. Marianini considers these effects as favourable to the Frank- 

 linian theory of electricity. In a note, he also quotes other 

 effects, which he thinks far more easily explained by the theory 

 of one electric fluid. In an electro-motive pair, if the negative 

 plate be more deeply immersed in the fluid, the effect is greater 

 than if the positive plate be immersed. If a plate of tin, or some 

 other metal, 18 or 20 square centimetres in surface, be formed, at 

 one side, with a narrow projecting band, and then placed so that 

 the plate is in one vessel of water (a), and the band in another (6) — 

 if then, a plate of zinc be placed in the vessel (6), and a plate of 

 copper in («), neither of them touching the metal — if then a 

 galvanometer be connected with the zinc and copper plates, a feeble 

 deviation will be obtained ; but if the zinc and copper plates be 

 reversed, a much stronger effect will be procured. 



*' It is in vain that I endeavour to explain this fact by the theory 

 of two electric fluids, since, if on the one hand, when the plate of 

 zinc is in (6), the passage is rendered difficult for the vitreous 

 fluid, and facilitated for the resinous fluid ; on the other, when 

 the copper plate is there, the passage is rendered difficult for the 

 resinous fluid, and facilitated for the vitreous. There is no reason, 

 therefore, for a difference of results. But in the theory of one 

 fluid, it is easy to conceive, that, in the first case, the electric fluid 

 which is diffused, as if by radiation, through the liquid, would 

 find the passage more difficult than in the second case, and con- 

 sequently the electro-magnetic effect, which is known to depend 

 principally upon the rapidity of the electric current, should be 

 less in the first case than in the second." — Ajin^ de Chimie, xlii. 131. 



9. Heated Air used in Iron Furnaces. — Heated air for blast 

 furnaces has been used for some time at the Clyde iron works, 

 and with great success. Experiments have proved that iron is 

 smelted by heated air with three-fourths of the quantity of coal 

 required when cold air, i.e., air not artificially heated, is employed 

 for that purpose, while the produce of the furnace in iron is at 

 the same time greatly increased. All the furnaces at Clyde iron 

 works are now blown with it. At these works, the air, before 

 it is thrown into the blast-furnace, is heated to 220° Fahrenheit, 

 in cast-iron vessels, placed on furnaces similar to those of steam- 

 engine boilers. It is expected, that a higher temperature than 

 220° will be productive of a proportionably increased effect. But 

 this is a subject of experiment. It is supposed that this improve- 



