424 
POPULAR SCIENCE REVIEW. 
along tlie sliores with cables moored out into the stream ; 
these were taken up in turn as the tube reached them and 
served for adjusting it to its resting-place in the towers. 
Thus prepared, with the aid of Captain Claxton and a large 
body of sailors, the operation of removal was commenced. 
An ineffectual attempt was made with the first tube on the 
evening of June 19, 1849. Next evening Mr. Stephenson, 
with Mr. Brunei, Mr. Locke, Captain Claxton, and some 
friends again took their places on the tube, watched by thou- 
sands of anxious spectators from every accessible point along 
the banks. Slowly as the tide rose the pontoons took the 
tube from its bearings, the land attachments were cut, and 
the tube swung majestically out into the stream, held by a 
radius chain extended up the shore. This was cut, and the 
tube slid slowly down the great guide cables, Mr. Locke and 
Mr. Brunei assiduously watching the application of the friction 
breaks, whilst from the top Mr. Stephenson signalled by flags 
to the various capstans on shore. As the buoyed ends of the 
other cables were reached they were attached ; the tube was 
brought up against a butt near the Anglesea tower, and on 
this, as a fulcrum, swung round to its position at the Britannia 
tower. It was hauled home here, and the other end glided 
into its place. Gradually, as the tide fell, the pontoons left 
their stupendous cargo safely resting on the bases of the towers. 
The tubes weighing 1,550 tons had now to be raised to a height 
of 100 feet. This was effected by three enormous Bramah 
presses,* placed at the top of the towers and worked by steam- 
engines. Massive flat-linked chains were suspended from the 
cross-heads of the presses in the towers, and attached to the 
ends of the tubes ; each link six feet long had a square shoulder 
by which it was attached to the cross-head by clips. As the 
* The hydraulic press improved and in- 
troduced into general use by Bramah acts 
upon a principle long understood, the appli- 
cation of which in the production of great 
pressure was suggested by Pascal in the 
middle of the seventeenth century. It consists 
of a cylinder, C, into which water is pumped 
at a considerable pressure, either by hand, 
or, as in the case of the bridges, by steam- 
engines. In the cylinder is a solid ram, R, 
sliding freely through a peculiar water-tight 
joint at the top, the invention of which is 
due to Bramah. H is the crosshead from 
which the chains were suspended. The water 
is pumped in through a small pipe (not shorvn) at a pressure of about three 
Fig. 3. 
