452 POPULAR SCIENCE MONTHLY. 



to the other. Tommasina contends that he has proved the existence of 



these chains of particles by experiments made with iron filings; and 



E. Malagoli,*in referring to Tommasina 's assertion, states that it can 



be witnessed in the case of brass filings placed between two plates of 



metal and immersed in vaseline oil, when a difference of potential is 



made between the plates. 



T. Sundorphf says he has confirmed Tommasina 's discovery of the 



formation of these chains of metallic particles in the coherer. The 



filings do not all cling together, but certain chains are formed which 



afford a conducting path for the current subsequently passed through 



the coherer from an external source. Accordingly, Tommasina 's 



method of causing decoherence in the case of filings of magnetic metals 



is to pull them apart by an external magnetic field; and he stated that 



decoherence can be effected more easily and regularly in this way than 



by tapping. Whilst on this point, it may be mentioned that C. TissotJ 



says that he has found that the sensitiveness of a coherer formed of 



nickel and iron filings can be increased by placing it in the magnetic 



field, the lines of which are parallel to the axis of the tube. According 



to MM. A. Blondel and G. Dobkevitch, this is merely the result of an 



increased coherence of the particles. 



{To be continued.) 



* II Nuovo Cimento, Vol. X., p. 279, 1899. 



fWied. Ann., Vol. LXVIII., p. 594, 1899; Science Abstracts, Vol. II., p. 

 757. 



XComptes Rendus, Vol. CXXX., p. 902, 1900; Science Abstracts, Vol. III., 

 p. 615. 



