CAI 
CAL 
be acceptable. Each of the caissons con- 
tained 150 loads of fir timber, and was of 
more tonnage than a man of war of 40 guns ; 
tiieir size was nearly 80 feet from point to 
point, and 30 feet in breadth; the sides, 
which were 10 feet in height, were formed 
of timbers laid horizontally over one an- 
other, pinned with oak trunnels, and framed 
together at all the corners, except the sa- 
lient angles, where they were secured by 
proper iron-work, which being unscrewed, 
would permit the sides of the caisson, had 
it been found necessary, to divide into two 
j)arts. These sides were planked across 
the timbers, inside and outside, with 3-inch 
planks, in a vertical position. The thickness 
of the sides was 18 inches at bottom, and 
15 inches at top ; and in order to strengthen . 
them the more, every angle, except the two 
points, had three oaken knee timbers pro- 
perly bolted and secured. These sides, 
when finished, were fastened to the bottom 
or grating, by 28 pieces of timber on the 
outside, and 18 within, called straps, about 
8 inches broad, and about 3 inches thick, 
reaching and lapping over the tops of the 
sides ; the lower part of these straps vvere 
dove-tailed to the outer curb of the grating, 
and kept in their places by iron wedges. 
The purpose of these straps and wedges 
was, that when the pier was built up suffi- 
ciently high above low-water-mark, to ren- 
der the caisson no longer necessary for the 
masons to work in, the wedges being 
drawn up, gave liberty to clear the straps 
from the mortices, inconsequence of which 
the sides rose by their own buoyancy, leav- 
ing the grating under the foundation of the 
pier. The pressure of the water upon the 
sides of the caisson was resisted by means 
of a ground timber or ribbon, 14 inches 
wide and 7 inches thick, pinned upon the 
upper row of timbers of the grating ; and 
the top of the sides was secured by a suffi- 
cient number of beams laid across, which 
also served to support a floor on which the 
labourers stood to hoist the stones out of tire 
lighters, and to lower them into the cais- 
son. The caisson was also provided with a 
sluice to admit the water. The method of 
working was as follows ; A pit being dug 
and levelled in the proper situation for the 
pier of the same shape as' the caisson, and 
about five feet wider all round ; the caisson 
was brought to its position, a few of the lower 
courses of the pier built in it, and smik once 
or twice to prove the level of the founda- 
tion ; then, being finally fixed, the masons 
worked in the usual methods of tide-work. 
About two hours before low water, the 
sluice of the caisson, kept open till then, 
lest the water, flowing to the height of 
many more feet on the outside than the in- 
side, should float the caisson and all the 
stone-work out of its true place, was shut 
down, and the water pumped low enough, 
without waiting for the lowest ebb of the 
tide, for the masons to set and cramp the 
stone-work of the succeeding courses. 
Then, when the tide had risen to a consi- 
derable height, the sluice was opened 
again, and the water admitted ; and as the 
caisson was purposely built but 16 feet 
high to save useless expense, the high tides 
flowed some feet above the sides, but with- 
out any damage or inconvenience to the 
works. In this manner the work proceed- 
ed till the pier rose to the surface of the 
caisson, when the sides were floated away 
to serve the same purpose at another pier. 
CAKILE, in botany, sea-rocket, a genus 
of the Tetrandia Siliculosa class and order. 
Silicle lanceolate, somewhat four-sided, con- 
sisting of two deciduous joints, witliout 
valves, and each containing a single seed : 
the lower joint with a tooth on each side at 
the tip. There are two species, viz. C. ma- 
ritima, found on the sea-coast of England, 
and C. ffiigyptiaca, a native of Italy and 
Egypt. 
CALAGUALA root, brought from Ame- 
rica for medicinal purposes, and has ac- 
quired considerable reputation on the con- 
tinent. It is supposed to be obtained from 
a species of polypodium. Its colour is 
brown, and partly covered with scales like, 
the roots of fein, and is hard and difficult to 
reduce to powder. It is asserted by Vau- 
quelin that it contains 
Woody fibre 
Gum 
Resui 
Sugar 
Starch 
Colouring matter 
Malic acid 
Muriate of potash 
Lime 
Silica. 
The mode of analysis may be thus described. 
Alcohol dissolves tlie resin and sugar. By 
evaporating the solution to dryness, and 
treating the residue with water, the sugar' 
is separated, and the resin left. Water 
dissolved the gum and the muriate of pot- 
ash, which were obtained by evaporation. 
Diluted nitric acid dissolved the starch and 
colouring matter, and let fall the former 
when mixed with four times its bulk of alco- 
hol. The woody fibre remained, which 
when incinerated left carbonate of lime, 
muriate of potash, and a little silica. As 
