for apenmg a Roadway under the Thames. S77 
Bnd, when a great body of quicksand gave way, and filled the 
drift, the miners soon overcame this obstruction, and were able 
to proceed until they were stopped, by a second irruption, 
which, in a few minutes, filled it. Nothing comes more satis- 
factorily in support of the system that is adopted here, than the 
result of the operations that were carried, under that circum- 
stance, to an extent of 1011 feet, and within 130 feet from the 
opposite shore. 
It is to be remarked, that, at the second irruption, on ex- 
amining the bed of the river, a hole was discovered 4 feet dia- 
meter, 9 feet deep, with the sides perpendicular,- — a proof that 
the body of quicksand was not extensive ; but what is most re- 
markable is, that this hole could be stopped merely by throwing 
from abo^^e^ clay yartly in bags and other materials : and, after 
pumping the water out under a head of 25 feet of loose ground, 
and 30 feet of water, the miners resumed the work, and pro- 
ceeded a little further ; but finding the hole at the first irruption 
increased, and the filling over the second very much sunk, the 
undertaking was abandoned. 
The character of the plan before us, consists in the mode of 
effecting the excavation, by removing no more earth than is to 
be replaced by the body of the tunnel, retaining thereby the 
surrounding ground in its natural state of density and solidity. 
In order so to effect an excavation 34 feet in breadth by 18 
feet 6. inches in height, the author of this plan proposes to have 
the body of the tunnel preceded by a strong framing of corres- 
ponding dimensions, as represented in the accompanying draw- 
ings (Plate IX.), and in the model proposed to be submitted 
for inspection. The object of this framing is to support the 
ground, not only in front of the tunnel, but at the same time 
to protect the work of excavation in all directions. The body 
of the' tunnel, which is to be constructed in brick, is intended 
to be fitted close to the ground (See Fig. 1-3.) ; and, in pro- 
portion as the framing is moved forward, so the brick-work 
is made to keep pace with it. But, as this framing could not 
be forced forward all in one body, on account of the friction 
of ks external sides against its surrounding earth, it is com- 
posed of eleven perpendicular frames which admit of being 
moved singly and independently of each other, in proportion 
as the ground is worked away in front. These several frames 
