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SCIENTIFIC RECREATIONS. 



The problem was solved the lamp was a fact. But hovy .can paper, 

 so easily burned, answer ? We will endeavour to explain. " A piece of 

 charred paper, cut into horse-shoe shape, so delicate that it looked like a fine 

 wire firmly clamped to the two ends of the conducting and discharging 

 wires, so as to form part of the electric circuit, proved to be the long- 

 sought combination." 



We will now explain the construction of this little lamp, which is 

 shown in the illustration (fig. 274) one-half of its actual size. The illuminating 

 is equal to ten or twelve ordinary gas jets. 



The manner in which the paper is prepared is, like many other very 

 important inventions, extremely simple, and, we may 

 add, almost costless. Cardboard will furnish us with 

 the loops, and these "horseshoes" are placed in layers 

 in an iron box with tissue paper between each. The 

 box is then hermetically sealed, and made red hot. 

 The carbonized paper remains till all the air has been 

 got rid of, and although it will burn freely to ashes in 

 atmospheric air, in the vacuum prepared for it it is 

 never consumed.- That is the plain fact the secret 

 of the Edison lamp. 



A vacuum can now be produced almost perfect. 

 It is of course impossible to extract every tiny particle 

 of air from the globes, but by the Sprengel pump, in 

 which mercury is employed, excellent vacuums are 

 obtained. Several very curious phenomena have been 

 observed in these vacuums, and the Royal Society has 

 been engaged upon their consideration. Another ad- 

 vantage of the vacuum, as applied by Edison, is that 

 little or no heat is generated. The electricity is all, 

 or very nearly all, converted into light. Thus the 

 glass globes remain almost unheated, and are un- 

 broken. 



The electric current passes along the wire, W, 

 and at a certain place marked B, the copper is 

 soldered to a platinum wire, which enters at C, and so by platinum clamps 

 into the horse-shoe, L. The return wire is similarly arranged ; the carbon 

 is enclosed in a glass bulb, GG, and all the air is extracted by the pumps ; 

 the end is then sealed up by melting it at F. 



The world is now in possession of a lamp for household use, and we 

 are surprised that it is not more extensively adopted in England. There 

 are some Swan lamps used in parts of the British Museum, and when we 

 have explained the application of the light, and the uses to which the motive 

 power can be applied, we shall, we believe, convince the most conservative 

 gas bill advocate that Edison's lamp is cheaper, safer, and far better in 

 illuminating power than gas, if the success of the electric lamp can be assured. 



Fig. 274. Edison's electric 

 lamp. 



