C A I 



CAIROAN, or Kair-wan, the Finis /lu^vjt'i of tbe 

 Itinerary, a walLd city of Africa, in t!ie ancient Bizacium, 

 nr modern Li ij;Join of Tunis, inferior in trade and in 

 rmmVi'- ■ of inhahit.ints only to Tunis, is fituatctl in a fandy 

 barren p'ain, 8 kagiRS W. of Sufa, and about tbc fanne 

 ■ii'.lancc S.W. of Hcrkla. In this city and its vicinity are 



■cral fragments of ancient archittfture. Its prefmt name 



. ms to be fynonymons with " Caravan," and might ori- 

 a!ly denote the phice where the Arabs had their principal 



,tioii in conquering this part of Africa. It is faid to have 

 i jn founded for this purpofe, and colonized by Akbah, 

 ti-.- Hucba, in the 50th year of tlie Hegira, A.D. <}~:>. 

 Notwiiiillanding the inconveniences of its lituation, which 

 renders it necefi'ary to obtain vegetable food from a great 

 diitancc, and to colleft a precarious fupply of rain-water in 

 cillerns or refervoirs, Akbah encompafled it with a wall, 

 enclofmga circumference of j6oo paces ; and in the fpace of 

 five years, the governor's palace was furrounded with a fuf- 

 ficient number of private habitations ; a fpacious inofque 

 was fupported by 500 columns of granite, porphyry, and 

 Numidian marble ; and Cairoan became the feat of learning, 

 as well as of empire. Under the government of Ibrahim 

 Ben Aglab, from whom was derived the dynally of the 

 Aglabites, in the year 184 of the Hegira, A.D. 800, its 

 buildings and inhabitants were very confiderably augmented; 

 and its inland iituation, 12 miles weft ward of the fea, pro- 

 tefted it from the Greek and Sicilian fleets. In the year 

 of the Hegira, 9^6, A.D. 1549, it hud its own fovereign, 

 who was an Arab ; but he was defpoiled of part of his do- 

 minions by Dragat, who commanded in the city of Tri- 

 poli for Soliman II. emperor of the Turks. N. hit. 35° 

 3'j'. E. long. 10° 13'. 



CAISIOMU, a town of the ifland of Cuba; 50 miles 

 E.S.E. of Villa del Principe. 



CAISSON, in Archiuaure, The praftice of building in 

 cainbns is a method fometimes adopted in laying the foun- 

 dation of bridges in very deep or rapid rivers. Thefe are 

 large hollow vcflels framed of llrong timbers, and made wa- 

 ter-tight, which being launched and floated to a proper 

 pofition in the river where the ground has been previoufly 

 excavated and levelled, are there funk. The piers of the 

 bridge are then built within them, and carried up above, or 

 nearly to the level of the water, when the fides of the 

 caifl'on are detached from the bottom, and removed ; the 

 bottom, compofed of a ilrong grating of timber remaining, 

 and ferving for a foundation to the pier. 



The mod confiderable work, which has come to our 

 knowledge, where caiffbns have been ufed, is in the building 

 of Wellminfter-bridge ; of thefe, therefore, a particular ac- 

 count may be acceptable. Each of the caiflbns contained 

 150 loads of fir timber, and was of more tonnage than a 

 man of war of 40 guns ; their fize was nearly So feet from 

 point to point, and jO feet in breadth ; the fides, which 

 were 10 feet in height, were formed of timbers laid hori- 

 zontally over one another, pinned with oak trunnels, and 

 framed together at all the corners, except the falient angles, 

 where they were fecured by proper iron-work, which being 

 unfcrewed would permit the fides of the caiffon, had it been 

 found neceflary, to divide into two parts. Thefe fides 

 were planked acrofs the timbers infide and outfide with 

 3-inch planks, in a vertical pofition. The tliicknefs of the 

 fides was 18 inches at bottom, and ijj inches at top; and in 

 order to (Irengthen them the more, every angle, except the 

 two points, had three oaken knee timbers properly bolted 

 and fecured. Thefe fides when finiihed were fallened to 

 the bottom or grating, by 28 pieces of timber on the out- 

 fide, and 18 within, called ftiaps^ about S inches broad, 



C A I 



and about 3 inches thick, reaching and lapping over the 

 t0])S of the fides ; the lower part o? thefe llraps were dove- 

 tailed to the outer curb of the grating, and kept in their 

 places by iron wedges. The purpofe of thefe itraps and 

 wedges was that when the pier was built up fntliciently high 

 above low-water-mark, to render the caldon no longer nt- 

 ceffary for the mafons to work in ; the wedges being drawn 

 up gave liberty to clear the ilraps from the mortices, in 

 confequcnce of which the fides rofe by their own buoyancy, 

 leaving the gi-ating. under the foundation of the pier. 



The preilure of the water upon the fides of the cailTon 

 was refilled by means of a ground timber or ribbon, 14 

 inches wide, and 7 inclus thick, pinned upon the upper 

 row of timbers of the grating ; and the top of the fides was 

 fecured by a fufficient number of beams laid acrofs, which 

 alfo ferved to fupport a floor on which the labourers ftood 

 to hoift the ftonei out of the lighters, and to lower them 

 into the caifTon. 



The caiilbn was alfo provided with a lluice to admit the 

 water. The method of working was as follows : A pit 

 being dug and levelled in the proper fituation for the pier 

 of the fame Ihape as the caiffon, and about five feet wider 

 all round ; the caiffon was brouu^ht to its pofition, a few of 

 the lower courfes of the pier built in it, and funk once or 

 twice to prove the level of the found.itlon ; then being 

 finally fixed, the mafons worked in the ufnal methods of tide 

 work. About two hours before low water, the fluice of 

 the caiffon, kept open till then, lell the water, flowing to the 

 height of many more feet on the outfide than the infide, 

 fhould float the caiflon and all the ftone work out ot its 

 true place, was flint down, and the water pumped low 

 enough, without waiting for the lovvell ebb of the tide, for 

 the mafons to fet and cramp the itone-work of the inccced- 

 ing courfes. Then when the tide had rifen to a confiderable 

 height, the fluice was opened again, and the water ad- 

 mitted ; and as the caiffon was purpofely built but 16 feet 

 high to fave uftlefs expence, the high tides flowed fome feet 

 above the fides, but without any damage or inconvenience 

 to the works. In this manner the work proceeded till the 

 pier rofe to the furface of the caiffon, when the fides w-ere 

 floated away to ferve the fame purpofe at another pier. 

 (Labclye's Defcription of Wellminller-bridge.) 



Caisson, in the Military Art, is iometimes ufed for a 

 chefl; ; and in particular for a bomb-chell. 



The caiffon is confidered as a fuperficial mine, or fourncaii. 



Caisson is alfo a covered waggon to carry bicad, or am- 

 munition. 



CAISTOR, in Gcosraphy. See Castor. 



CAISTRUS, in Ancient Geography, Kaijlcr, a fmall rivet* 

 of Afia Minor in Ionia, formed by the union of two 

 branches, which had their fources in mount Tmolus, and 

 flowing by the fouth-weft, watered Metropohs or Ephefus, 

 near which it difcharged itfelf into the fea. It is called at 

 prefent by the Turks " Kitchik Meinder," or the Little 

 Meander. Virgil refers to it, 



" Jam varias pelagi volucres, et qux Afia circum 

 Dulcibus in flagnis rimantur prata Cayltri." 



Georg. 1. I. 



CAITAIA, in Zoology, the name under which Marc- 

 graave noUces Jlmia J'ciuren of Gmelin. 



CAITHNESS, in Gcogniphy, fometimes denominated 

 the fhire of Wick, is the moll northerly county of Scotland. 

 Its S. W. border unites with the county of Sutlierlaid, and 

 the remainder is wafhed by the waters of the Pcntland-frith,. 

 and the German Ocean. Thrs dlUntt, includes an area of 

 about ,55 miles from N. to S. by 22 miles from eait to weft. 

 Mr. Pennant dtfcribe? the country as a large morafs inter- 



fperfed 



