ons in
any way. The real diaphragm may be removed altogether. It is sufficient to
replace it by a few grains of iron filings thrown on the pole covered with
a piece of pasteboard or paper. Such a telephone works distinctly although
feebly; but any slender flexible disk, metallic or not, spread over across
the opening of the cover of the instrument, with one or two tenths of a
gramme (three grains) of iron filings, will yield results of increased and
even ordinary intensity. This is the iron filing telephone, which is
reversible; for a given magnetic field there is a certain weight of iron
filings for maximum intensity. It appears thus that the advantage of the
iron diaphragm over iron filings reduces itself to presenting in a certain
volume a much more considerable number of magnetic molecules to the action
of the field. The iron diaphragm increases the telephonic intensity, but it
is by no means indispensable.

* * * * *

ON ELECTRO-DISSOLUTION, AND ITS USE AS REGARDS ANALYSIS.

By H.N. WARREN, Research Analyst.

On the same principle that electro-dissolution is used for the estimation
of combined carbon in steel, etc., I have lately varied the experiment by
introducing, instead of steel, iron containing a certain percentage of
boron, and, having connected the respective boride with the positive pole
of a powerful battery, and to the negative a plate of platinum, using as a
solvent dilute sulphuric acid, I observed, after the lapse of about twelve
hours, the iron had entirely passed into solution, and a considerable
amount of brownish precipitate had collected at the bottom of the vessel,
intercepted by flakes of graphite and carbon; the precipitate, having been
collected on a filter paper, washed, and dried, on examination proved to be
amorphous boron, containing graphite and other impurities, which had become
chemically introduced during the preparation of the boron compound. The
boron was next introduced into a small clay crucible, and intensely heated
in a current of hydrogen gas, for the purpose of rendering it more dense
and destroying its pyrophoric properties, and was lastly introduced into a
combustion tubing, heated to bright redness, and a stream of dry carbonic
anhydride passed over it, in order to separate the carbon, finally pure
boron being obtained.

In like manner silicon-eisen, containing 9 per cent. of silicon, was
treated, but not giving so satisfactory a r