Mr. W. H. Barlow on a new Electrical Machine. 429 



that they might be employed in producing an electrical ma- 

 chine at once cheap and simple ; and I have accordingly had 

 a machine constructed p. 



as follows:— abed is a 

 wooden frame which 

 carries two wooden rol- 

 lers, R and r. The 

 lower roller, R, is about 

 six inches diameter, 



and a handle, H, is at-^ ^J^f 



tached to the axle. ^-* "^ 



The upper roller is 

 about three inches dia- 



^ 



meter. 



A band of thin sheet '— 

 gutta percha about four 



inches wide is made to pass round the rollers, fitting them 

 very tightly. CC are two cushions covered with silk, and 

 connected together so as to press the gutta percha at their 

 upper extremities, and opening towards their lower extremi- 

 ties at an angle of about 20°. When the handle of the ma- 

 chine is turned, causing the gutta percha band to pass at a 

 moderate velocity in the direction denoted by the arrow, elec- 

 tricity is given off at P, about three or four inches below the 

 cushions; and if a conductor be applied, as shown in the 

 sketch, the apparatus may be used as a common electrical 

 machine. 



The quantity of electricity developed increases with the sur- 

 face of gutta percha; and from the energy exhibited by so 

 small a band, it is evident that considerable power might be 

 obtained by a more extended application of this material. 



I observed that gutta percha may be excited both positively 

 and negatively. 



If a strip about two feet long and two inches wide be laid 

 on a surface and rubbed, the two extremities when suspended 

 in the air repel each other, and the electricity developed is 

 that termed "resinous." But if the strip of gutta percha be 

 folded double and rubbed, the upper side exhibits " resinous," 

 and the lower side " vitreous " electricity, and the two extre- 

 mities attract each other. 



I am, Gentlemen, 



Your obedient Servant, 



W. H. Barlow. 



P.S. Since writing the above, John Westmoreland, one of 

 the workmen in the establishment of Mr. Davis, optician, at 



