But one great step has been made in the diver's art by the
introduction of the chemical system of respiration, the invention
of Mr. Fleuss. He has succeeded in devising a perfectly portable
apparatus, containing a chemical filter, by means of which the exhaled
breath of the diver is deprived of its carbonic acid; the diver
also carries a supply of compressed oxygen from which to add to the
remaining nitrogen oxygen, in substitution for that which has been
burnt up in the process of respiration. Armed with this apparatus,
a diver is enabled to follow his vocation without any air-tube
connecting with the surface, indeed without any connections whatever.
A notable instance of a most courageous use of this apparatus was
afforded by a diver named Lambert, who, during one of the inundations
which occurred in the construction of the Severn tunnel, descended
into the heading, and proceeding along it for some 330 yards (with the
water standing some 35 feet above him), closed a sluice door, through
which the water was entering the excavations, and thus enabled the
pumps to unwater the tunnel. Altogether, on this occasion, this man
was under the water, and without any communication with those above,
for one hour and twenty-five minutes. The apparatus has also proved to
be of great utility in cases of explosion in collieries, enabling
the wearer to safely penetrate the workings, even when they have been
filled with the fatal choke-damp, to rescue the injured or to remove
the dead.