118 An account of the Electro-Magnetic Engine. 



city in the former is in a state of motion, whilst in the latter it is in a 

 state of equilibrium. As it exists in the metals and fluids alluded to, it 

 gives forth a feeble but continuous electric shock. This electrical cur- 

 rent has the effect of heating the connecting wire, and imparting to it a 

 magnetic virtue. This species of electricity, developed by the connec- 

 tion of metals with acids, has received the names of galvanic and 

 voltaic, from Galvani and Volta, the original discoverers.* 



From the period of the discovery, by Professor Orsted, of Copen- 

 hagen, in 1820, of the peculiar influence exerted by the electrical cur- 

 rent on the magnetic needle, no possible doubt could be any longer 

 entertained of the connection between magnetism and electricity. And 

 the varied exertions of scientific men of different countries have suc- 

 ceeded in directing attention to a new branch of study, which does not 

 date beyond twenty years ago; the influence of which on practical 

 life promises to become more and more beneficial. To the exertions of 

 Schweiggers we are indebted for the multiplier, or galvanometer ; by- 

 means of which the relative strength of different currents may be tested. 

 Ampere succeeded in shewing, that a wire, spirally coiled, possesses all 

 the properties of an ordinary magnet, as long as the electrical currents 

 circulate therein. Sturgeon, of Woolwich, was the first who, in 1826^ 

 produced a powerful electro-magnet, by coiling wire spirally round 

 a bar of soft iron, and discharging an electrical current through the 

 wire. Henry and Ten-Eyk, in America, have already produced mag- 

 nets capable of raising two thousand pounds weight, and upwards. It 

 therefore appears, that, whilst it has been hitherto a matter of much 

 difficulty to procure magnets of any considerable power, we need at 

 present nothing more than a bar of soft iron, horse-shoe shaped, round 



* If the electrical current be brought to bear on a fluid, it resolves it into its two principal 

 constituent parts : thus, for instance, water is thereby resolved into oxygen and hydrogen, 

 sulphuric acid into sulphur and oxygen, and blue vitriol, or vitriol of copper, into sulphuric 

 acid and oxide of copper : and this separation of the parts is peculiar, in so far as the oxygen, 

 or body most resembling it, invariably attaches to the zinc, whilst the other constituent 

 element attaches itself to the copper ; but in the canal between the zinc and copper no trace of 

 this action is visible. On applying blue vitriol diluted with water, the sulphuric acid of 

 the salt and the oxygen of the water will be recognised on the zinc, and the oxide of 

 copper of the former and hydrogen of the latter on the copper. The oxygen and zinc combine, 

 and give oxide of zinc, and this resultant combined with the sulphuric acid yield sulphuretted 

 oxide of zinc; whilst the hydrogen in combination with the oxygen contained in the oxide 

 of copper forms water; and we thus arrive at a clear precipitate of copper. The above- 

 named substances, copper, zinc, water, and blue vitriol are the bodies whose agency is princi- 

 pally employed in the galvano-magnetic machine. 



The copper which is thus obtained is perfectly pure, and covers at least one half of the loss 

 of zinc occasioned by the process. — Algemeine Anzciger der Deutschen. 



