CAMPHOR, ARTIFICIAL. 



CAXAL. 



boning point are both higher, and when treated with anhydrous phos- 

 phoric a. id it yields, u might be expected from iu composition, 

 fc"> (CJBLJ, instead of rymiiu (CjJl,.). obtained under the same 

 cimuuatance* from laurel camphor. The crystal* aUo have a dim-rent 

 f..rm. are harder, and more brittle. In other respects it resemble* the 



; 



l, or liquid camphor, U obtained from the young trees of 

 aromatira, by incising the lark. It U a mixture in 

 variable proportion*, of the hydrocarbon borniSeue with borneol or 

 olid Borneo camphor. 



Camphor exist* in amall quantity in many plant*, more especially in 

 those of the natural order Labiala ; for example, lavender, rosemary, 



TThe various kinds, though they may be otherwise identical, act very 

 unequally upon polarised hght Ordinary camphor causes the rays to 

 rotate to the right hand : Borneo camphor does the same, but more 

 powerfully, while that obtained from the tfatritaria parthenitim, A 

 plant of the natural order Comporittr, and a species of chnmomile 

 (common feverfew), causes them to rotate to the left-hand. Camphor 

 from the Labiate has no action whatever on the polarised rays. Cam- 

 phoric acid also causes rotation in a direction similar to that induced 

 by the camphor that yields it. For instance, the acid obtained from laurel 

 camphor possesses deztro-rotation, while a solution of the camphoric 

 aciil of the niatricaria camphor, exhibits levo-rotation. A mixture of 

 i ha* no rotatory power, thus bearing an interesting resemblance 

 to the different iaomeric modifications of tartaric acid. 



Besides its position in the Materia Medica, camphor is used to some 

 extent as a perfume. 



CAMPHOR. ARTIFICIAL. (Tl-BPENTlXE.J 



CAMPHOR OIL. [CAMPHOR.] 



r.VMPHoHAMICACID. [CAMPHOR.] 



CAMPHORAMIDE. [CAMPHOB.! 



CAMPHORANILE. [CAMPHOR.] 



CAMPIK iRANILIC ACID. [CAMPHOR.] 



CAMPHORKSINK. A black resinous matter of unknown compo- 

 sition, formed, along with other products, by the action of iodine upon 

 camphor. 



i A M PHORIC ACID. [CAMPHOR.] 



CAMPHORIC ETHER. [CAMPHOR.] 



CAMI'HOIUMIDK. [CAMPHOR.] 



( -AMPIIOVIXIC ACID. [CAMPHOR: Campho-elliylle Arid.] 



I'AMPHKONE. [CAMPHOR.] 



M>A I'.A I.SAM. [BALSAM.] 



VAL. A word used by modern engineers to express, in an 

 exclusive sense, the bodies of water and the works provided for the 

 purpose of forming artificial navigable courses ; the word channel being 

 applied to the ordinary water-courses ; conduit, to the artificial water- 

 courses established for the distribution of that fluid for municipal 

 consumption. Canals are also formed for the purposes of Irrigation 

 [IIIUKATION]; but in speaking of them it is customary to prefix the 

 specific title, and always totdistinguish them as Irrigation Canals. 



The execution of works for the purposes of improving the existing 

 internal navigation of rivers, or for creating artificial courses for that 

 purpose, dates from the very earliest antiquity ; and it may also be 

 observed to have taken place amongst nations whose civilisation 

 ha* remained, in all other respects, in a very rudimentary state. Thus 

 the Assyrians, Egyptians, and Hindoos, have from time iinm.-i,,..u .1 

 booted of the works executed by their government*, for both irriga- 

 tion and navigation. The canal* of China have long been famous, and 

 indeed some of the details of Chinese construction, as their rolling 

 bridges for instance, have served as models for Europeans ; whilst the 

 hydraulic works of the Mexicans and Peruvians justly excited the 

 admiration of their Spanish conquerors ; who, l.y the way, must have 

 been acquainted with the first steps in the hi-tory of Italian hydraulic 

 engineering, which took place precisely in the dominions of tlie 

 house of Austria, near Milan. The formation of the canal >!. la I 

 anna was, indeed, the first great advance made by European engineers 

 in this branch of engineering, and it was there that Leonardo da Vinci 

 for tin- firat time, introduced the use of locks to regulate the level of 

 tin- water in different reaches of the canal. About 1642, the canal 

 do Briare, in the centre of France, was funned, under the patronage of 

 Sully ; in 1681 the first summit level canal between two oceans was 

 opened by mean* of the Canal du Midi ; in England, the navigation of 

 the Itchin. between Winchester and Southampton, was opened about 

 the same peri.. I. but it was not until nearly a century later that the 

 execution of our lines of internal navigation assumed, under the 

 guidance of such men as Brindlcy, Smcaton, Telford, Rennic, &<-.. the 

 commercial and political importance they now possess. In the following 

 notice, however, it U not proponed to follow the historical develop 

 roent of the system of canal navigation ; but rather to trace broadly 

 the principle* which regulate the practice of the best engineers, illus- 

 trating them with references to the most celebrated work* in various 

 ... 



Canal* for the purpose* of artificial navigation are of three principal 

 descriptions, according to the nature of the locality in which they are 

 formed, and to the immediate object* they are designed to effect. 

 There are ganal* established for the avowed object of allowing sea- 

 going Teasels to proceed to towns situated at some distance from the 



coast, which are known as dip canal*. There are lateral canals, or 

 those established on the banks of rivers, in order to obviate, the natural 

 obstacles to a barge navigation, whether occasioned by the irregu- 

 larities in the volume of water flowing in the natural channel, or l.y the 

 occurrence of rapids, falls, or other interferences with the I! 

 water, or with the regularity of th<- im-i-'a bed; sometimes also, 

 lateral canals are formed iu order to cut off the bends of tin- 

 natural water courses. Lastly, there are the 



canal*, or those established for the purpose of connecting existing lines 

 of navigation on the respective sides of a central elevated <1 

 dividing the water-sheds of a country. Many of the operations 

 required for these various descriptions of canals are common to them 

 all ; but each of them presents distinctive features which render it 

 necessary to consider them in detail. 



Ship canals, being designed to accommodate vessels used for deep- 

 sea navigation, must naturally be made of much larger dimen-i"iis 

 than the canals exclusively devoted to purposes of inland navigation. 

 Thus, the canal from the Severn to Gloucester has a width of 7 

 and a depth of 18 feet, and it U able to receive vessels of 400 tons 

 burden ; the ship canal opened between Caen and the sea, has a 

 clear width on the water-line of 100 feet, and is also inten< 

 be used by sailing vessels of 400 tons burden ; whilst the great North 

 Holland canal, between Amsterdam and the Xieuw-diep, is not less 

 than 124J ft. wide on the water line, with a depth of 20 ft. 9 in., 

 and is able to receive sailing vessels of about 1400 tons burden. The 

 dimensions of the Caledonian canal are 115 ft. 6 in. on the water line. 



Caledonian Canal. 



and 20 ft. depth of water. Some of the lateral canals, however, liave 

 widtln upon the water liue as great as those above quoted : but in no 

 caw is thoir depth made to exceed, in any notable manner, about 

 8 feet ; and the construction of the locks, and of the entrances to the 

 tidal basing, is the most materially affected by this condition. 



In forming a ship canal, great care is required in the selection of the 

 position of the entrance from the sea, in order to secure free access 

 at all times of the tide, and a permanent depth of water in the outer 

 harbour. The entrance must, in fact.be placed in a sheltered roil 

 stead, and in such a position as shall ensure its immunity from tin- 

 action of any littoral current able to transport much alluvial matter: 

 at the same time there must theoretically be a sufficient Hiijiply of 

 clear waU-r to allow of an efficient scour in the harbour. It i 

 essential that the direction of the entrance should be such as to 

 obviate any possible inconvenience from the prevailing winds, so far as 

 the entry of ships into the harbour, or their departure thcm-efrom. i- 

 concerned. By the application of a good system of dredging, and e\ . n 

 by creating au artificial scour, it is possible to correct any n 

 tendency of a harbour to become silted up ; but there are no simple 

 artificial means by which the dangers resulting from a harbour's being 

 exposed to the direct action of a head sea can be obviated; so 

 after all, the exposition of the entrance to a ship canal, with iei 

 to the position of the prrvailhrr winds, is the most essential ;> 

 be considered in its selection. If, therefore, the outlet of such I 

 to the sea should be situated upon an exposed coast, it will be neces- 

 sary to form an outer harbour ; and to establish the entrance locks to 

 the .artificial navigation under the shelter of the jetties or piers thus 

 carried forward. When the entrance is, however, fitu.it. .1 in a pro 

 tected position, it must be designed upon the same piim -iple.< with 

 reference to the set of the currents, and to the facilities to be given 

 to the passage from the canal to the open navigation, which will 

 hereafter be described in the case of ordinary canal entrances. 



The lock gates of ship canals are necessarily of much larger dim. -n 

 sioiu than those of either of the other description of canals: fur not 

 only are the vessels they are required to pass larger than the ordinary 

 river or canal craft, but they often require to resist greater diffei 

 of levi-1 on their upper or lower widen, in a of the rise and 



fall of the tides. On the Caledonian canal, the clear width 'of Un- 

 lock chamlK-rs, at the level of the coping is 40 ft. ; and a gate inteii.h il 

 to pass a 1400 ton vesseLmust be at least 50 ft. wide at the narrowest 

 part; and whereas, ordinary canal looks are made to overcome <1 ill. i 

 ences of level of 8 ft., it may often hap|-n that the difference of level 

 :. the inner basin ami the- outer tidal surface of the entrain . 

 harbour of a ship c.uial. may attain a* much as from 24 to 30 f. 

 height. In the North Holland canal the engineers have very wisely 

 constructed the locks with two passages, one for large vessels, the 

 other for small ones ; thus obviating the necessity for wasting the time 

 and water required to fill the large lock when a smaller one wouM 

 suffice, and also, avoiding the unnecessary fatigue of the large g 

 The mode of constructing lock gates, and the precautions to be taken 

 t,. pn-\eiii thafa i hange of form, are described in the subsequent part 

 of this article under the sub-head, 



