Origin of Dynamo-electric machines. 13 



lead ornaments with copper by using a solution of 

 copper in a similar manner. And in 1836 Mr. 

 De la Rue found that copies might be taken in 

 copper of engraved copper-plates by the electro- 

 depositing process. Faraday discovered magneto- 

 electricity in the year 1831, by rotating a disc of 

 copper between the poles of a magnet, and he has 

 stated that the first successful result he obtained was 

 so small that he could hardly detect it. This simple 

 experiment was the origin of the magneto-electric \ 

 machine, and many of these machines are now used 

 for producing the electric light, and for depositing 

 nickel, copper, silver, and gold, instead of by the 

 voltaic battery. These, and other engines, thermic, 

 magnetic, electric, &c., will probably, ere long, be 

 constructed on as large a scale, and as many in 

 number, as the present steam engine. 



The discovery in olden times of the attractive 

 properties of a fragment of iron ore, was the basis , 

 of the invention of the mariner's compass, which 

 greatly improved navigation, and led to nearly all 

 the chief maritime discoveries which have since been 

 made. The sciences of magnetism and geometry^ 

 form the basis of the art of navigation, and haveA 

 thus made our great foreign commerce possible../ 

 The discovery of magnetism enabled sailing vessels 

 to venture freely out of sight of land, and to traverse 

 the wide ocean with even greater safety than to sail 

 'near the shore. By its means Columbus crossed the N 

 Atlantic Ocean and discovered America. By its 



