Chemical Science. 



171 



22. Table of Thermoelectrics by Professor dimming. — The fol- 

 lowing table of thermoelectrics is by Professor dimming : they being 

 used two together, each substance is positive to all below, and 

 negative to all above. The voltaic series, and the order of conductors 

 of electricity and heat, are added merely to shew that the thermo- 

 electric series has no accordance with either of them. 



Ann. Fhil. N.S. vi. 170. 



23. Horizontal Plate Electrical Machine. — Dr. Hare, of Pennsylva- 

 nia, has suggested and practised a new mode of mounting the plate of an 

 electrical machine, by which it is made to afford negative electricity as 

 readily as positive, without losing any of the advantages which the plate- 

 machine has over the cylinder. The plate is made to revolve hori- 

 zontally, and is supported on an upright iron bar, about an inch in 

 diameter, which rises through a table on which the machine stands. 

 The bar rests beneath the table on a brass step, and is furnished with 

 a wheel and band, by which motion is given to the machine. Its 

 upper end is fastened by a block of wood and cement, into a glass 

 cylinder 4| inches in diameter and 16 inches long, which, being open 

 only at the lower end, forms a perfect insulation. A brass cap sur- 

 mounted by a screw and shoulder is cemented on to the cylinder, 

 and the plate is fastened on by means of the screw, a nut, and discs 

 of cork. Thus the plate, which is 34 inches diameter, is mounted ; 

 and two cushions, of which there are two pair, placed opposite to 

 each other, as in the common machine, and the conductors are 

 mounted in a similar way, except that wood is used in place of iron. 

 The two rubbers connect together by an arched brass rod, and the 



