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XLIII. Intelligence and Miscellaneous Articles. 



ON THE REFLEXION OF RAYS OF ELECTRICAL FORCE FROM PLATES 

 OF METAL AND OF SULPHUR. BY PROF. KLEMENCIC, IN GRATZ. 



HPHE author has undertaken to investigate the reflexion of the 

 -*- rays of electrical force at a dielectric plate of sulphur and at a 

 zinc plate, both qualitatively and quantitatively ; and to compare 

 also in this respect the behaviour of these rays with those of light. 



In investigating the rays, he used secondary inductors with 

 interposed thermopile, as has been already described in a previous 

 paper (Phil. Mag. vol. xxx. p. 284). Two inductors were used this 

 time — the one as a standard, the other as the proper movable 

 secondary inductor. 



The reflexion took place against a sulphur plate, the dimen- 

 sions of which were 120 centim. by 80 by 7, and which was 

 made up of twelve bricks ; the dimensions of the zinc plate were 

 the same except in the matter of thickness, which was far less. 

 In addition to this, the author investigated the portion of the 

 rays transmitted by the plates. The experiments on the reflexion 

 of metals were completed by observations on a wire grating, and 

 on a round zinc plate. The dimensions of the reflecting-plate and 

 of the mirror permitted the investigation only of the incident 

 angles 30° and 65°. 



Between the reflexion at the zinc plate and that of the sulphur 

 plate, it has been found that there was a difference, which qualita- 

 tively corresponds to the deportment of the rays of light. The 

 intensity of the reflexion is different according to the direction of 

 vibration of the rays. With the sulphur plate there is a powerful 

 reflexion under all angles of incidence, if the vibrations are at 

 right angles to the plane of incidence. It is otherwise with rays 

 in which the vibrations are parallel to the plane of incidence. In 

 this case a faint reflexion is found only with small angles of inci- 

 dence ; the intensity of the same increases with increasing angle 

 of incidence ; and at 60° to 65° no perceptible reflexion could be 

 established with the methods here employed. This fact agrees 

 very well with the optical relations, in so far that from the refrac- 

 tive indices of sulphur there is, in fact, a polarizing angle of 

 between 60° and 65°. As regards the question of the direction of 

 vibration in polarized light, the conclusions which result from these 

 experiments are the same as those found by Troughton (' Nature/ 

 xxxix. p. 391). It was further observed that the intensity of the 

 ray transmitted by the sulphur plate was the opposite of that of 

 reflexion. 



Although for individual angles of incidence the results obtained 

 by calculations with Fresnel's formula for intensity are in good 

 agreement, yet, in general, this does not hold. Some remarkable 

 phenomena occur which do not harmonize with the behaviour of 



