in Magnetism and Electricity. 103 



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

 diameter. 



78. When the intensity armature (71) was placed in the cy- 

 linder, the combination of the machines remaining the same as 

 in the preceding experiments (76), the alternating current from 

 the armature melted 7 feet of No. 16 iron wire 0085 of an inch 

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



79. The illuminating-power of the electricity from the inten- 

 sity armature is, as might be expected, of the most splendid de- 

 scription. Two rods of gas-carbon, half an inch square, were 

 placed in the carbon-holders of the beautiful apparatus for regu- 

 lating the electric light, recently invented by M. Foucault, be- 

 hind which was fixed a parabolic reflector 20 inches in diameter, 

 so adjusted as to cause the rays of light to diverge from it at a 

 considerable angle. When the electric lamp was placed at the 

 top of a lofty building, the light evolved from it was sufficient to 

 cast the shadows from the flames of the street-lamps a quarter of 

 a mile distant upon the neighbouring walls. When viewed from 

 that distance, the light was a very magnificent object to behold, 

 the rays proceeding from the reflector having all the rich efful- 

 gence of sunshine. 



80. A piece of the ordinary sensitized paper, such as is used 

 for photographic 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 exposed for a period of one minute to the direct 

 rays of the sun, at noon, on a very clear day in the month of 

 March. 



81. The extraordinary calorific and illuminating powers of 

 the 10-inch machine are all the more remarkable from the fact 

 that they have their origin in six small permanent magnets, 

 weighing only 1 lb. each (12), and only capable, at most, of sus- 

 taining collectively a weight of 60 lbs. ; while the electricity 

 from the magneto-electric machine which was employed in exci- 

 ting the electromagnet was, of itself, incapable of heating to 

 redness the shortest length of iron wire of the smallest size ma- 

 nufactured. 



82. The production of so large an amount of electricity was 

 only obtained (as might have been anticipated by the physicist) 

 by a correspondingly large expenditure of mechanical force, as 

 the machine when in full action absorbed, as nearly as could be 

 estimated, from eight to ten horse-power. When the 2i-inch 

 magneto-electric machine (58) was substituted for the l|-inch 

 machine, in the combination before described (76), the magnetism 

 developed in the electromagnet of the 10-inch machine was ex- 



