I. ELECTRICAL MACHINES ETC. 



SECTION 10. ELECTRICITY. 



WEST- GALLERY, GROUND FLOOR, ROOM F. 



I. APPARATUS FOR PRODUCING AND MAINTAIN- 

 ING DIFFERENCES OF ELECTRICAL POTEN- 

 TIAL. 



a. FRICTION AND INDUCTION MACHINES. 



1233. Electrical Machine, having ebonite plate 3 feet in 

 diameter. Frederick Guthrie, F.R.S. 



This machine gives sparks 13 inches long. 



1233a. Large Electrophorus, with shellac plate, 360mm. 

 diameter. Warnibrunn, Qui/itz, 8? Co. s Berlin. 



1234. Carre's Electric Machine. Prof. W. F. Barrett. 



This is an induction machine or continuous electrophorus, but the loss from 

 the inductor is renewed by a small attached frictional machine. 



1234a. Froment's Electric Pendulum. 



The pendulum is kept in motion by a current passing round the electro- 

 magnet which lifts a small weight that is released as the pendulum descends, 

 A control clock is associated with the pendulum. 



1234b. Crystal of Tourmaline, mounted to show 

 Pyro-Electricity. 



This crystal during heating or cooling exhibits polarity at its extremities. 

 It i? pivoted on a diamond cup. 



1234c. Electrical Machine, by Singer, used by Mr. Francis 

 Ronalds in his early experiments in the discovery of the electric 

 telegraph ; described in his work on the electric telegraph, 

 dated 1823. 



Kew Committee of the Royal Society, Kew Observatory. 



It is an ordinary cylinder machine of blue glass, standing on glass columns. 



1235. Bertsch's Machine. Frederick Guthrie, F.R.S. 



A negatively excited sheet of ebonite leans against a revolving disc of the 

 same material. On the other side of the revolving disc, one above and one 

 below, are electric rakes. The conductor in connexion with the lower rake 

 becomes negatively charged, the other one positively. 



39508. R 



