232 
carries it twenty feet along a railway, to the place for depositing 
the earth, and after emptying it carries it back on its board, that 
it may be let down while the other is coming up filled. The 
place, into which the earth is thrown, is a large wooden receiver, 
which is erected in the manner of a bridge. In the bottom of 
this receiver are several holes, which can be opened and closed 
by means of slides. The wagons destined for carrying away the 
earth, drive underneath such a hole, the slide then is drawn back, 
and the wagon is filled with earth and drives off. Up to this 
time none but silicious earth has been dug out of the tunnel, 
and this was appropriated to the filling up of the swampy ground, 
near Southwark. But now they find clay, which is used in burn¬ 
ing bricks. The machinery, by which the buckets are hoisted 
and lowered, and that moves the pump, is set in motion by a 
species of steam-engine, called the expansive engine, an invention 
of Mr. Brunei. I did not perfectly comprehend its mechanism, 
and could only perceive that it occupies a very small space, and 
acts with great facility ; there are two boilers and two machines, 
one of which is unemployed, but can immediately be set in mo¬ 
tion, whenever any thing happens to the other, so that nothing 
may stop the work. 
Around the wooden scaffold, stairs run down to the bottom of 
the pit. My guide, Mr. Armstrong, who inspects the work 
under Mr. BrunePs direction, conducted me. When arrived at 
the bottom of the pit, we found ourselves at the entrance of the 
tunnel, which then ran already, one hundred and twenty feet 
under ground, to the bed of the Thames. It was conceived that 
about one-third part of the work had been completed. The tunnel 
consists of two vaults for two passages, one of them is for car¬ 
riages passing in, and the other for those going out. Along the 
partition wall of those two vaults, there is on each side a somewhat 
elevated side-walk for pedestrians; this wall is open in some 
places in order to admit of a communication between both walks. 
It is lighted by means of portable gas, which is contained in cop¬ 
per barrels. 
The manner that the work is conducted, cannot be clearly 
explained without a drawing. The scaffold, upon which the 
workmen stand who are employed in digging out the earth, con¬ 
sists of thirty-six small boxes, lying in three rows above each 
other. This scaffold is at the end of the tunnel, and rests exactly 
against the earth to be taken away. There are three men in each 
box, one to break the ground with a pick-axe, the other to shovel 
it out of the box, and the third to throw it on a cart, in which it 
is carried into the pit, whence it is raised in the buckets. For 
the safety of the workmen, cross-tim 1 ers are used to prop up the 
earth that is to be dug out. The fin>* workman, on beginning 
