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Scientific Intelligence . 
conceived the idea of keeping the rubber hot, by fixing it in a 
hollow half cylinder of copper, supported by a hollow copper 
tube, at the lower end of which was placed a small spirit lamp, 
whose burner consists of only one thread of cotton. The prime 
conductor was also heated in a similar manner, being supported 
by a hollow glass tube, at the bottom of which another small 
spirit-lamp was placed. Mr Ronalds remarks, that a cylinder 
machine thus constructed is always effective. He supposes, that 
heat assists the excitement, by promoting the oxidation of the 
amalgam. — Ronalds on an Electrical Telegraph , p. 25. Lond. 
1828. 
14. On the Production of Electricity by Pressure. — From a 
series of experiments on this subject, M. Bccquerel concludes, 
that all bodies assume two different electric states by pressure 
that in two bodies which are perfect conductors, this state of 
equilibrium ceases the moment the pressure is removed, but if 
one be a bad conductor, the effect of the pressure continues for 
a longer or a shorter time ; that the pressure alone maintains 
the equilibrium of the two fluids placed in each of the surfaces, 
for if the pressure be diminished, and at the end of a certain 
time, the bodies be removed from the compression, they will be 
found to have the electricity due only to the remaining pressure ; 
that heat modifies the development of electricity in a particular 
manner ; that the intensity of the electricity increases, at first, 
directly as the pressure, and that it is probable this proportion 
diminishes at high pressures, as the bodies lose their power of 
being compressed. Finally, it is rendered probable, that the 
light which is disengaged in powerful concussions, is due to the 
rapid recombination of the two electricities developed on the sur- 
faces, at the moment of compression. — Quarterly Journal , 
No. xxx. p. 368. 
15. Development of Electricity by two pieces of the same 
Metal.* — M. Avogrado has discovered, that if two pieces of the 
same metal are plunged, at different instants, into an acid, which 
acts upon them, the piece first introduced will act as the most 
positive metal to the other. 
