Mr. H. Wilde's Researches in Magnetism and Electricity. 1 51 



net of the electro-magnetic machine, the electricity from the latter 

 melted 8 inches of the same-sized iron wire as was used in the pre- 

 ceding experiment, and a length of 24 inches was made red-hot. 



When the electro-magnet of a 5-inch machine was excited by the 

 2-1-inch magneto-electric machine, the electricity from the 5-inch 

 electro-magnetic machine melted 15 inches of No. 15 iron wire 0*075 

 of an inch in diameter. 



The author having found that an increase in the dimensions of 

 the machines was accompanied by a proportionate and satisfactory 

 increase of the magnetic and electric forces, a 10-inch electro-mag- 

 netic machine was constructed : the weight of its electro-magnet is 

 nearly 3 tons, and the total weight of the machine is about 4^- tons. 

 The machine is furnished with two armatures — one for the produc- 

 tion of "intensity"-, and the other for the production of " quantity"- 

 effects. 



The intensity armature is coiled with an insulated conductor con- 

 sisting of a bundle of thirteen No. 11 copper wires, each 0*125 of an 

 inch in diameter. The coil is 376 feet in length, and weighs 232 lbs. 



The quantity armature is enveloped with the folds of an insulated 

 copper-plate conductor 67 feet in length, the weight of which is 

 344 lbs. These armatures are driven at a uniform velocity of 1 500 

 revolutions per minute, by means of a broad leather belt of the strong- 

 est description. 



When the direct current from the lf-inch magneto-electric ma- 

 chine, having on its cylinder six permanent magnets, was trans- 

 mitted through the coils of the electro-magnet of the 5 -inch electro- 

 magnetic machine, and when the direct current from the latter was 

 simultaneously, and in like manner, transmitted through the coils of 

 the electro-magnet of the J 0-inch machine, an amount of magnetic 

 force was developed in the large electro-magnet far exceeding any- 

 thing which has hitherto been produced, accompanied by the evolu- 

 tion of an amount of dynamic electricity from the quantity armature 

 so enormous as to melt pieces of cylindrical iron rod 15 inches in 

 length, and fully one-quarter of an inch in diameter. With the same 

 arrangement, the electricity from the quantity armature also melted 

 15 inches of No. 11 copper wire 0*125 of an inch in diameter. 



When the intensity armature was placed in the magnet cylinder, 

 the electricity from it melted 7 feet of No. 16 iron wire 0*065 of an 

 inch in diameter, and made a length of 21 feet of the same wire red-hot. 



The illuminating power of the electricity from the intensity arma- 

 ture is, as might be expected, of the most splendid description. When 

 an electric lamp, furnished with rods of gas-carbon half an inch 

 square, was placed at the top of a lofty building, the light evolved 

 from it was sufficient to cast the shadows from the names of the 

 street-lamps a quarter of a mile distant upon the neighbouring walls. 

 When viewed from that distance, the rays proceeding from the re- 

 flector have all the rich effulgence of sunshine. 



A piece of the ordinary sensitized paper, such as is used for photo- 

 graphic printing, when exposed to the action of the light for twenty 

 seconds, at a distance of 2 feet from the reflector, was darkened to 

 the same degree as was a piece of the same sheet of paper when ex- 



