CAN 
CAN 
C A N 
CAMPHOROSMA, in botany, stinking 
ground pine ; a genus of the tetrandria order, 
in the monogyma class of plants, ranking in 
the natural method under the 12th order, 
hoieraces. The calyx is pitcher-shaped aud 
indented ; there is no corolla; and the capsule 
contains a single seed. It is reputed cephalic 
and nervine ; though little used in modern 
practice. It takes the name from its smell, 
which bears some resemblance to that of 
camphor. There are five species. Of these 
the principal is, 
Camphorosma monspeliensis, which grows 
by the road-side in Languedoc, and especial- 
ly about Montpelier, it has been produced 
as a specific for the dropsy, and asthma. 
CANAL, a kind of artificial river, made 
for the convenience of water-carriage. 
The Dutch, > or if we can believe the re- 
lations of travellers, the Chinese, who inhabit 
a country vastly more extensive than that of 
the Dutch, have shewn the great advantages 
resulting from canals to a trading people. 
There are several large canals in France ; 
that of Briere begun under Henry IV. and 
finished under Lewis XIII. establishes a com- 
munication between the Loire and the Seine 
by the Loing. There are forty-two sluices 
upon it. But the greatest and most wonder- 
ful work of that kind, and at the same time 
one of the most useful, is the junction of the 
two seas, by the canal of Languedoc, pro- 
posed under Francis I. but not finished till 
the time of Lewis XIV. 
The operations necessary for making arti- 
ficial navigations or canals, depend on the 
situation of the ground, the connection with 
rivers, and the ease with which water can be 
obtained. When the ground is naturally 
level, and unconnected with rivers, the exe- 
cution is easy, and the navigation is not liable 
to be disturbed with tloods: but when the 
ground rises and falls, and cannot be reduced 
to a level, artificial methods of raising and 
lowering vessels must be employed. Tem- 
porary "sluices are sometimes used for 
raising boats over falls or shoals in rivers by 
a very simple operation. Two pillars of 
masonry-work with grooves, are fixed, one on 
each bank of the river, at some distance be- 
low the shoal. The boat having passed these 
posts, planks are let down across the river by 
pulleys into the grooves, by which the water 
is dammed up to a proper height for allowing 
the boat to pass up the river over the shoal. 
The Dutch frequently make use of inclin- 
ed planes or rolling-bridges upon dry land, 
along which their vessels are drawn from the 
river below into the river above ; this was 
the method employed by the ancients, and 
is still used by the Chinese, who are said to 
be ignorant of the nature and utility of locks. 
These rolling-bridges consist of a number of 
cylindrical rollers which turn easily on pivots ; 
and a mill is commonly built near at hand, 
so that the same machinery may serve a 
double purpose of working the mill and draw- 
ing up vessels. 
Before a canal is undertaken, the following 
circumstances : edpire consideration. 
1st. Places to be benefited in point of trade. 
Trade being the grand source from which 
adventurers in canal schemes expect to derive 
their great profits, such towns, places &c. 
must be included in the line of a canal, to 
which the safe, expeditious, and easy con- 
veyance of merchandise, and consequent en- 
largement of commerce, will be of moment. 
These can be fixed upon only by an accurate 
survey and knowledge of the v country through 
which the canal is intended to pass. 
2dly. The supply of water, fic. It is almost 
needless to mention the absolute necessity of 
a supply of water for a canal, which must be 
in requisite quantities in the summit, or reser- 
voirs, which may be supplied by the neigh- 
bouring springs ; or if these fail, water must 
be thrown up by engines from a lower level. 
Reservoirs are large bodies of water col- 
lected together for the use of such parts of 
the canal as are likely to be deficient; into 
which it is let by sluices, when and where 
wanted. 
The quantity of water requisite for the use 
of a canal depends in a great measure upon 
the quantity of trade carried on. A lock- 
ful of water must be lost every time a boat 
passes through, which, in a lock whose length 
in the chamber is seventy-five feet, breadth 
seven feet, and lift six feet, will be 125 cubic 
yards of water; which quantity, multiplied 
by the number of boats likely to pass through j 
the summit lock, will give an idea of the i 
waste of water. Allowance also must be 
made for exhalation and accidents. 
The most eligible level is certainly that 
which has the least fall and the fewest ob- 
structions, and is best adapted to the face of 
the country. 
The soil most favourable for a canal is 
clay ; the most unfavourable, sand. As 
soils approach more or less to the quality of 
clay or sand, in such proportion are they to 
be preferred for holding water. 
Of the expence of execution little can be 
said, as it entirely depends on the extent, the 
several works, &c. which can be accurately 
known only by an actual survey and estimate, 
the total of which will of course be consider- 
ed previous to undertaking works of such 
magnitude. It may be proper to observe 
generally, that many locks, bridges, or aque- 
ducts, much tunneling, unfavourable soil, &c. 
will of necessity incur great expences. 
Lastly. The mode of execution. The fore- 
going particulars having been attended to, 
it becomes necessary to enumerate the seve- 
ral works, useful and necessary, in the execu- 
tion of a canal. 
For the passing and repassing of boats, 
there are various expedients, some of which 
have been noticed ; but experience confirms 
the use of locks, when it becomes necessary, 
by artificial means, to raise or let down boats 
from one level to another. 
' A lock is a large basin, or, more properly, 
a long square cistern, placed lengthways in a 
river or canal, inclosed by upper and lower 
gates. The lock should be lined with walls 
of strong masonry on each side, and at. the 
bottom ; or if wood, stout oak piles should be 
used, shod with iron, and lined with two 
inch and a half or three inch oak plank, with 
a floor of the same materials, laid on oak- 
sleepers, dove-tailed and spiked into the up- 
right piles. 
The use, or locking down, is thus mana- 
ged : the lock being full to the level of the 
upper water, the gates are then shut, includ- 
ing tire boat to be lowered. The water in 
the lock is drawn off ; in part first, by means 
of the paddles in the gates, and completely 
by the gates being opened ; when the boat, 
2t)5 
being upon a level with the lower water, is 
able to proceed upon its passage. For as- 
cending, or locking up, the boat being in the 
lock, the lower gates are shut : the lock is 
then filled with the upper water, first by the 
sluices, and finally by the gates being open- 
ed: thus the vessel is on a level with the 
upper water, and may immediately proceed. 
In the first figure (see Plate) we have a 
perspective view of part of a canal, with a 
vessel within a lock, on the upper level of 
the water. The second figure shews a sec- 
tion of an open lock, with a vessel about to- 
enter. A, B, in the former figure, are llocd- 
gates ; each of which consists of two leaves 
resting upon one another, so as to form an 
obtuse angle, in order to resist the pressure of 
the water. A, when shut, prevents the water 
of the superior canal from falling into the 
lock, and B sustains the water in the lock- 
I), in the second ligure, is the subterraneous 
passage by which the water passes from the 
upper level into the lock when the sluice d is 
opened ; and C is the passage by* which the 
water in the lock is let out when the sluice c 
is raised ; and thus the vessel in the lock is 
brought on a level with the lower part of the 
canal. 
CANARINA, in botany, a genus of the. 
order monogyma, belonging to the hexandria. 
class of plants. The calyx is six-leaved ; co- 
rolla six-cleit, bill-form. There are 2 species. 
CANARIUM, in botany, a genus of the 
dioecia order, in the pentandria class of 
plants. Its characters are, that it has male 
and female flowers ; that, in both, the calyx 
has two leaves, and the corolla consists of 
three petals: the fruit is a drupa with a three- 
cornered nut. There is but one species. 
CANCER, in astronomy, one of the 12 
signs, represented on the globe in the form 
ot a crab, and thus marked (eg) in books., 
It is the fourth constellation in the starry zo- 
diac. The reason generally assigned for 
its name as well as figure, is a supposed resem- 
blance which the sun’s motion in this sign- 
bears to the crab’s. As the latter is said 
to walk backwards, so the former, in this, 
part of his course, begins to go backwards,, 
or recede from us. By others, the disposi- 
tion of stars in this sign is supposed to have 
given the first hint to the representation of 
a crab. It gives name to a quadrant of the 
ecliptic, viz. 
Cancer, tropic of, in astronomy, a lesser 
circle of the sphere parallel to tire equator, 
and passing through the beginning of the 
sign Cancer. 
Cancer, in medicine, a roundish, unequal, 
hard, and livid tumour, generally seated in 
the glandulous part of the body, supposed to 
be so called because it appears at length 
with turgid veins shooting out from it, so as 
to resemble, as it is thought, the ligure of a 
crab-fish ; or, others say, because, like that 
fish, where it has once got, it is scarcely pos- 
sible to drive it away, b’ee Medicine. 
Cancer, in zoology, a gemiA of insects 
belonging to the order of insecta aptera. 
The generic characters are these: they have 
eight legs, (seldom ten or six) besides two 
large claws which answer the purpose of 
hands. 'J Ley have two eyes at a consider- 
able distance from each other, and for the 
most part they are supported by peduncull 
or footstalks : the eyes are elongated and 
moveable. They have two clawed palpi, 
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