in
vain, for it refused to budge. Mr. Chavatte therefore had recourse to
a dredge with vertical axis, constructed as follows:

Upon a square axis, A B (Pl. 2, Figs. 1, 2, and 3), provided with
double cross braces, C D, and strengthened by diagonals, were riveted,
by their upper extremities, two cheeks, G H, whose lower extremities
held the steel plates, I J I' J', which, in turn, were fastened to the
axis, A B, by their other extremities. These plates were so inclined
as to scrape the surface of the ground over which they were moved.
They each carried two bags made of coarse canvas and strengthened by
five strong leather straps (Figs. 2 and 4). To the steel plates were
riveted two plates of iron containing numerous apertures, through
which passed leather straps designed for fastening thereto the lower
part of the mouth of the bags. That portion of the mouth of the latter
that was to remain open was fastened in the same way to two other
plates, X Y, X