674 



NATURE 



\Oct. 24. 1878 



EDISON'S INVENTIONS 



THE fertility of Mr. Edison's inventive genius has 

 frequently been referred to recently, though the 

 attractive and popular nature of the phonograph has had 

 the effect of throwing some almost equally important 

 inventions into the shade. We propose, with the aid of 

 the Scientific American, copies of which have been sent 

 us by Mr. Edisoq, to draw attention to a few of these 



other inventions ; the illustrations which we are able to 

 give have also been kindly sent us by Mr. Edison himself. 

 Mr. Edison's laboratory, in size and external appear- 

 ance, resembles a country church. The interior, however, 

 is not so church-like. The first apartment is a reception 

 room, on the right of which is the private office, contain- 

 ing a large library of scientific works. Beyond these 

 there is a large room containing materials and a number 

 of glass cases filled with physical and chemical apparatus, 



Fig. I. — Ediscn's Harimnic Engine. 



The machine shop at the rear is furnished w'ith the best 

 of machinery and tools, and is kept constantly in opera- 

 tion im carrying out the plans of Mr. Edison. On the 

 second floor there is a single spacious room, which is 

 the laboratory proper. Here, upon the walls, are shelves 

 which are thickly studded with bottles, jars, and boxes, 

 containing a multitude of substances, both corhmon and 

 rare. It is said to be a chronic habit of Mr. Edison 



to purchase every newly discovered substance, so that 

 it will be at hand should it be required. Here also 

 is the carbon relay, the progenitor of all existing carbon 

 telephones, "microphones," and other instruments de- 

 pendent on the changeable conductivity of carbon under 

 a varying pressure. 



One of the earlier of Mr. Edison's inventions is the 

 electro-motograph ; a telegraphic instrument in which 



Flu. 2. — Edison's Naw Carbon Rheostat. 



the sounder is operated without magnets. A strip of che- 

 mically prepared paper is laid upon a metallic surface, 

 which is connected with one of the battery wires, and a 

 platinum faced spring which is attached to the other 

 battery wire is taken in the hand and pressed firmly on 

 the paper strip ; at the same time force is applied in the 

 -direction of the length of the strip. A telegraph key is 

 placed in the electric circuit, and when the current passes. 



through the paper the salt contained by it is instantly 

 decomposed, so that it acts as a lubricant, permitting the 

 spring to slide easily on the paper while the current 

 passes, but immediately the current is broken the friction 

 is sufficient to stop the spring. 



The best solution for saturating the paper is made by 

 dissolving i lb. of sulph. soda in i gallon of water. Any 

 of the sodium salts will answer. 



