Royal Institution of Great Britain. 465 



tube open at both ends), of the same length ; and that in tlie latter 

 ttiey were the same with those of a stopped pipe of the same length. 

 March 23. — Dr. Ritchie on the Temperature of Fluids undergo- 

 ing Voltaic Decomjiosition, and on the Equality of ihe Electro-mag- 

 netic Powers of Solid and Liquid Conductors. 



Dr. Ritchie first showed experimentally that all conductors of 

 voltaic electricity possessed equal electro-magnetic effects. A piece 

 of charcoal deflected the needle as much as a metallic wire, conduct- 

 ing the same quantity of voltaic electricity ; and a cylinder of water 

 suffering decomposition deflected tlie needle with tlie same force as 

 a metallic wire, passing through the axis of the cylinder and form- 

 ing a part of the same circuit. As another proof of the same fact, 

 two pieces of charcoal were made to rotate about the magnet, similar 

 to the original experiment of Mr. Faraday. But the most striking 

 part of the whole was the experiments on the rotation of a hollow 

 column of water. In one of the experiments the water was made to 

 rotate about the pole of the magnet, carrying the box in which it 

 was contained along with it. In the second the water was made to 

 circulate round the magnet, whilst the vessel in which it was con- 

 tained remained fixed. 



The second part of the lecture was employed in examining the 

 temperature of different parts of a liquid suffering decomposition. 

 With regard to water, the temperature of the water in contact with 

 the positive pole rose higher than that in contact with the negative 

 pole; whilst the temperature of the water in the middle rose higher 

 than either of the extreme portions. The reverse was observed with 

 metallic solutions. These phaenomena depend on the specific heats 

 of the substances liberated at the two poles, and seem to open a new 

 field for experimental research*. 



March 30. — Mr.Faraday on the Evolution of Electricity, naturally 

 and artificially, by the inductive action of the Earth's Magnetism f. 



By dispensing with any other magnet tlian the earth, Mr. Faraday 

 still found that, when moving metals cut the terrestrial magnetic 

 curves, currents of electricity were either produced, or tended to be 

 produced, in them. A piece of soft iron in the direction of the dij), 

 when introduced into a hollow helix, evolved a current of electricity. 

 The mere inversion of the helix, without iron, in the direction of the 

 dip produced the same effect. On revolving a circular copper plate 

 perpendicular to, or inclined to, the dip, electricity of one kind could 

 be collected at its edges, and of another kind at its axis, thus render- 

 ing it a new electrical machine. Merely carrying a wire to and fro 

 through the air so as to intersect tlie magnetic curves was shown to 

 produce electricity. 



Mr. Faraday then considered natural phaenomena probably depen- 

 dent upon these terrestrial actions, and stated that wherever currents 

 existed, as in rivers, seas, Src, elcc:ric currents might result; and 

 even suggested tiiat the lines of e(] lal magnetic variation probably 

 f)we some of their flexures over the ocean to these causes. In speak- 

 ing of the diurnal revolution of theglobe, lie showed experimentally 

 • See p. 450. | See p. 4-17. 



N.S. Vol. 11. No. CO. June IB,*!?. 3 O that 



