502 Notices of Scientific Works. [Oct.. 



be suspended between the poles of a sufficiently powerful magnet it 

 would set equatorially, or east and west instead of north and south. 

 Of all diamagnetic bodies bismuth has attracted the most attention, 

 owing to the comparative power which it exhibits. Its diamagnetic 

 properties, although vastly inferior to the paramagnetism of iron, 

 are yet sufficiently marked to enable its properties to be observed 

 with small j>ermanent magnets weighing a few ounces ; whilst a 

 bismuth needle freely suspended will set itself parallel to the wires 

 of a galvanometer. The property is not one possessed permanently 

 by the bismuth, but is simply induced by the proximity of the 

 magnet, nothing being communicated which the bismuth can carry 

 away. 



Having shown almost complete antithesis between the mag- 

 netism of iron and bismuth, the question naturally arose, Is this 

 extended to polarity ? Faraday worked long and earnestly at this 

 question, and we believe to the last he was not satisfied that the 

 question of polarity in diamagnetic bodies was settled, although the 

 experiments with AVeber's exquisitely beautiful apparatus were tried 

 in his presence by Professor Tyndall. In a letter to Matteucci, 

 dated November 2, 1855, Faraday wrote, " All Tyndall's results are 

 to me simple consequences of the tendency of paramagnetic bodies 

 to go from weaker to stronger places of action, and of diamagnetic 

 bodies to go from stronger to weaker places of action, combined with 

 the true polarity or direction of the lines of force in the places of 

 action." On the other hand, it would appear as if these two philo- 

 sophers were looking at the subject from entirely different points of 

 view. Faraday had his mind fixed on lines of magnetic force, the 

 use of which, as true representations of nature, he said never failed 

 him ; whilst Tyndall limited his view to that doubleness of action 

 in which the term polarity originated. But these were apparent 

 differences only, not differences in reahty, for in the letter just 

 quoted, Faraday said, " I differ from Tyndall a good deal in phrases, 

 but when I talk with him I do not find that we differ in facts. 

 That phrase polarity in its present undefined state is a great 

 mystifier." 



Considerable space is given to the description of the beautiful 

 instrument devised by M. Weber in order to submit this question 

 to a crucial test, the design of which was ably carried out by 

 M. Leyser, of Leipzig. Clear engravings of it are given, and the 

 experiments are described in full detail. With it not only has dia- 

 magnetic polarity been proved to exist in the case of bismuth, but 

 the same result was obtained with cylinders of calcareous spar, 

 statuary marble, phosphorus, sulphur, heavy glass, distilled water, 

 bisulphide of carbon, and other non-conductors of electricity, remov- 

 ing the scruples of those who saw in the first experiments of this 

 sort an action produced by induced currents. By these experiments, 



