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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. 



This machine gives sparks 13 inches long. 



1233a. Priestley's Electrical Machine. Royal Society. 



1267. Winter's Machine, with 18-inch ebonite plate and 

 condenser attached, for the accumulation of electricity. 



Elliott Brothers. 



Large Double-Plate Vulcanite Friction Electric Ma- 

 chine. Dr. W. H. Stone. 



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

 diameter. Warmbrunn, Quilitz, fy Co., 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 replaced by a small attached frictional machine. 



1234:a. Froment's Electric Pendulum. 



Prof. W. F. Barrett. 



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 in connexion with the pendulum. 



1234b. Crystal of Tourmaline, mounted to show 

 Pyro-Electricity. Prof. W. F. Barrett. 



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

 It is pivoted on a diamond cap. 



