14.48 per cent.; alumina, 17.31 per cent.; lime and magnesia, traces. The
iron peroxide is partly soluble in hydrochloric acid, the alumina entirely
so as silicate. The scouring paste, therefore, is composed of 54 per cent.
fatty (palm oil) acid, 10 per cent. jeweler's rouge, 32 per cent.
pumice-stone powder.

* * * * *




SOUND SIGNALS.


In Appleton's "Annual Cyclopædia" for 1883, Mr. Arnold B. Johnson, Chief
Clerk of the Lighthouse Board, contributes a mass of very interesting
information, under the above title. His descriptions of the most approved
inventions relating thereto are interesting, and we make the following
extracts:

The sound signals generally used to guide mariners, especially during
fogs, are, with certain modifications, sirens, trumpets, steam-whistles,
bell-boats, bell-buoys, whistling buoys, bells struck by machinery,
cannons fired by powder or gun cotton, rockets, and gongs.

_Gongs._--Gongs are somewhat used on lightships, especially in British
waters. They are intended for use at close quarters. Leonce Reynaud, of
the French lighthouse service, has given their mean effective range as
barely 550 yards. They are of most use in harbors, short channels, and
like places, where a long range would be unnecessary. They have been used