e!" and certainly the shining brass helmet and
staring large plate-glass eyes fairly warranted such a suggestion. The
principles of the diving-bell and of the diving-helmet are too well known
to require explanation: but the practical utility of these machines is
daily proved. Even while we now write, it has been ascertained that the
foundations of Blackfriars Bridge are giving way. The bed of the river,
owing to the constant ebb and flow of its waters, has sunk some six or
seven feet below its level since the bridge was built, thus undermining
its foundation; and this effect, it is presumed, has been greatly
augmented by the removal of the old London Bridge, the works surrounding
which operated as a dam in checking the force of the current. These
machines, also, are constantly used in repairing the bottom of docks,
landing-piers, and in the construction of breakwater works, such as those
which are at present being raised at Dover Harbor.

Among other remarkable objects in the museum of natural history we
recognized, swimming upon his shingly bed under a glass case, our old
friend the Gymnotus Electricus, or Electrical Eel. Truly, he is a
marvelous fish. The power which animals of every description possess in
adapting themselves to external and adventitious circumstances, is here
marvelously illustrated, for, notwithstanding this creature is surrounded
by the greatest possible amount of artificial circumstances, inasmuch as
instead of sporting in his own pellucid and sparkling waters of the river
Amazon, he is here confined in a glass prison, in water artificially
heated; instead of his natural food, he is here supplied with fish not
indigenous to his native country, and denied access to fresh air, with
sunlight sparkling upon the surface of the waves--he is here surrounded by
an impure and obscure atmosphere, with crowds of people constantly moving
to and fro and gazing upon him; yet, notwithstanding all these
disadvantageous circumstances, he has continued to thrive; nay, since we
saw him ten years ago, he has increased in size and is apparently very
healthy, notwithstanding that he is obviously quite blind.

This specimen of the Gymnotus Electricus was caught in the river Amazon,
and was brought over to this country by Mr. Potter, where it arrived on
the 12th of August, 1838, when he displayed it to the proprietors of the
Adelaide Gallery. In the first instance, there was some difficulty in
keeping him alive, for, whe