Page:Popular Science Monthly Volume 63.djvu/456

452 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. Sundorph 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. Tissot 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.