I regret that time will not admit of my giving any description of the
modes of "cut and cover" which have been proposed for the performance
of subaqueous works; sometimes the proposition has been to do this
by means of coffer-dams, and with the work therefore open to the
day-light during execution, and sometimes by movable pneumatic
appliances. Consideration of subaqueous works necessarily leads the
mind to appliances for diving, and although its date is considerably
anterior to 1862, I feel tempted, as I believe the construction is
known to very few of our members, to say a few words about the diving
apparatus known as the "Bateau-plongeur," and used at the "barrage"
on the Nile. This consists of a barge fitted with an air-tight cabin
provided with an air-lock, and having in the center of its floor
a large oval opening, surrounded by a casing standing up above the
water-line. In this casing, another casing slides telescopically, the
upper part of which is connected to the top of the fixed casing by
a leather "sleeve." When it is desired to examine the bottom of the
river, the telescopic tube is lowered till it touches the bottom, and
then air is pumped into the cabin until the pressure is sufficient to
drive out the water, and thus to expose the bottom. This appears to be
a very convenient arrangement for shallow draughts of water.
Reverting for a moment to Mr. Stoney's work, I may mention that he
uses for the greatest depths he has to deal with, when preparing the
bed to receive his blocks, a diving apparatus which (while easily
accessible at all times) dispenses with the necessity of raising and
lowering, needed in an ordinary diving-bell to allow of the entrance
and exit of the workmen. Mr. Stoney employs a bell of adequate size,
from the summit of which rises a hollow cylinder, furnished at the
top with an air-lock, by which access can be obtained to the submerged
bell. Beyond the general improvement in detail and in the mode
of manufacture, and with the exception of the application of the
telephone, there is probably not much to be said in the way of
invention or progress in connection with the ordinary dress of the
diver.