Mr. W. G. Armstrong on the Electricity of Effluent Steam. 51 



, The insulation of the boiler was effected by lifting the en- 

 gine with screw-jacks, until the wheels were raised about six 

 inches above the rails, and then supporting it upon four insu- 

 lators which rested upon logs of timber. Each insulator con- 

 sisted of three separate pieces of baked wood, coated with 

 pitch, and having layers of pitch and brown paper placed be- 

 tween them. The middle piece was made larger than the 

 other two, so as to project beyond them, and thereby increase 

 the surface without adding to the height of the insulator, 

 which would have been dangerous ; and the three pieces when 

 put together formed a block, of which a representation is an- 

 nexed (fig. 1.). 



As soon as the engine was placed on the insulators, the 

 boiler was filled with water, and Fig. l. 



the fire lighted, and as the press- 

 ure gradually rose in the boiler, 

 the steam was occasionally suf- 

 fered to escape. 



The engine indicated no elec- 

 tricity whatever so long as the 

 steam was confined in the boiler, 

 but became negatively electri- 

 fied as soon as any escape was permitted. A very trifling 

 escape proved sufficient to render the negative electricity of 

 the boiler sensible, and when the steam was very freely dis- 

 charged the negative development became exceedingly power- 

 ful. The sparks never much exceeded an inch in length, but 

 were very large and brilliant, and, owing no doubt to the 

 magnitude of the body from which they were drawn, they pro- 

 duced effects fully equal to those obtained by the use of an 

 average-sized Leyden jar. Some idea of their potency may 

 be formed from the fact, that when not more than half an 

 inch in length, they easily ignited a piece of cotton wool filled 

 with powdered resin. 



The greatest care was taken to ascertain whether the ex- 

 tent of the electrical development was at all dependent upon 

 the density of the steam in the boiler ; and it was found that 

 when the discharge from the valve was so regulated in the 

 different trials as to render the actual quantity or voeigJtt of 

 steam ejected in a given time as unitbrm as possible, the ne- 

 gative electricity of the boiler increased a little v/\lh the press- 

 ure, but the positive electricity, drawn by the pointed con- 

 ductor from tlie issuing steam, increased eiiannoiisly as the 

 density of the steam wasaugiiieiited. After the fire had been 

 extinguished at the close of the experiments, and the pressure 

 had subsided to six or eight pounds on the square inch, sparks 



E 2 



