AQUEDUCT -AQUINAS. 



219 



ribs or arches, and these resting^ on pillars of stone. 

 The iron being much lighter than stone arches, this 

 is one reason why the pillars have been reduced ap- 

 parently to such slender dimensions. They are quite 

 strong enough, however, as experience has proved. 

 The whole length of the aqueduct is about 1000 

 feet, and consists of 19 arches, each 45 feet span. 

 The breadth of the pillars at the top is eight feet, 

 and the height of the four middle ones is 115 feet to 

 the springing. The pillars have a slight taper, the 

 breadth of the middle ones at the base being 15 feet. 

 The height from the surface of the water in the Dee 

 to that in the canal was to be 126 feet eight inches. 

 The channel for the water consists of cast iron plates, 

 cast with flanches, and these screwed together with 

 -bolts ; they are represented in the drawing, between 

 the arched ribs and the railing. The lines there show 

 the joinings of the different plates. In order to pre- 

 serve as much water-way as possible, the channel is 

 made the full width of the canal and towing path, 

 and the latter projected over one side, and supported 

 inside by posts resting on the bottom of the canal. 

 The aqueduct of Chirk was designed by the same able 

 engineer, and serves also to convey across a valley 

 the waters of the same canal. This aqueduct was 

 the first in which any iron was employed. Hitherto 

 the channel for the waters had been constructed of 

 stone, or partly of stone and partly of clay puddle, 

 which it was generally found very difficult to keep 

 water-tight for a length of time. It was deter- 

 mined, therefore, by Mr Telford to try the effect of 

 cast iron, and to lay it at first only in the bottom. 

 The plates were accordingly laid directly over the 

 sprandrel walls, which they served to bind together, 

 and united by flanches and screws. The sides of the 

 channel were built with stone facings and brick heart- 

 ing laid in water-lime mortar. This plan has suc- 

 ceeded completely, and the quantity of masonry in the 

 aqueduct was thereby greatly reduced. The aque- 

 duct itself is 600 feet long, and 65 feet high above 

 the river, consisting of ten arches, each 42 teet span. 

 The piers are ten feet thick. The aqueduct of Slate- 

 ford serves for conveying the waters of the Edinburgh 

 ml Glasgow Union Canal across the valley of the 

 Water of Leith at Slateford. It is an elegant struc- 

 ture, and very similar in the plan to that of Chirk, 

 only that the water channel is composed entirely, the 

 sides as well as the bottom, of cast iron, which is 

 moreover built in with masonry. It is about 500 feet 

 in length, and consists of eight arches, each 45 feet 

 sjiHii ; and the height of the canal is about 70 feet 

 above the level of the river. On this canal another 

 aqueduct of the very same construction occurs in cross- 

 ing the valley of the Almond, and having several 

 more arches. There are, in different parts of the 

 country, various other aqueducts, which might be de- 

 H:rilx;d ; but our limits preclude our enlarging upon 

 them ; and it is the less necessary, as, excepting the 

 formation of the water-way, these structures differ 

 nothing in their design or the principle of their con- 

 struction from ordinary bridges, particularly those 

 that are undertaken not so much with the view of 

 crossing rivers as of raising up the level of the road 

 itself entirely out of the valley, an object now be- 

 come of great importance, from the improvements 

 which have taken place within the last half century 

 on all our roads, and the refined notions which have 

 in consequence begun to prevail as to the rates of 

 travelling, and, what conduces most essentially to this 

 object, the levels of the road. Formerly people 

 were content to traverse slowly all the inequalities of 

 the country through which the road might pass, de- 

 fending into the valleys, and mounting the steepest 

 acclivities. Now, however, a road is thought imper- 

 fect, and quite behind the standard of improvement, 



unless every rise greater than one in fifteen or one in 

 twenty feet be cut down. In crossing the valleys, 

 therefore, it is not enough now that we build & bridge 

 in all respects sufficient for crossing the stream itself; 

 we must raise it nearly to a level with the ground or. 

 each side of the valley ; and this circumstance gives 

 rise to new and very extensive works of this kind, 

 which formerly never would have been thought of. 

 Of these we may just instance the splendid bridge of 

 one arch of 140 feet span, built over the Den Burn at 

 Aberdeen, to form a new access into that town ; also 

 the beautiful bridge of Cartland Craigs, built by Mr 

 Telford, over the little stream of the Mouse, on the 

 new road from Glasgow to Carlisle, consisting of three 

 arches 50 feet span, and elevated 130 feet above the 

 bed of the stream. More recently the introduction of 

 railways opens a new and still wider field for the skill 

 and talents of the engineer in the erection of such 

 works. Aqueduct, in anatomy, is a bony canal or 

 passage, in the os petrosum, supposed to contribute 

 to the purposes of hearing. 



AQUILA ; the chief city of Abruzzo Ulteriore II., on 

 the chain of the Apennines, with a population of 

 7500. It is the ancient Amiternum, and the birth- 

 place of Sallust. It is of military importance as the 

 point where several roads meet, and contains a cita- 

 del which capitulated, 1815 and 1821, on the first 

 appearance of the Austrians. (See Abruzzo.) In 

 1703, it suffered most severely by an earthquake. 

 Lon. 13" 25' E. ; lat. 42 19' N. 



AQUILEIA, also AGLAR ; in the time of the Roman 

 emperors, a flourishing commercial city on the Adri- 

 atic sea, and the Timavus, in Upper Italy. Marcus 

 Aurelius made it, A. D. 168, the principal fortress of 

 the empire. It was the key of Italy against the bar- 

 barians, and, on account of its wealth, was sometimes 

 called the second Rome. It was also the seat of a 

 patriarch, whose diocese, in 1750, was divided into 

 the archbishoprics Udine and Gorz, afterwards Lay- 

 bach. In 452, it was destroyed by Attila. The in- 

 habitants fled to the islands, on which Venice was 

 afterwards built. An inconsiderable city afterwards 

 arose here, which now belongs to the Austrian king- 

 dom Illyria (circles Trieste and Friuli). The inha- 

 bitants (1500) support themselves, chiefly, by a trifling 

 fishery, and foreigners visit the place on account of 

 the Roman antiquities to be found there. 



AQUINAS, St Thomas, a celebrated scholastic divine, 

 descended from the counts of Aquino, in Calabria, in 

 the kingdom of Naples, was born in the year 1224. 

 He acquired the rudiments of education at the school 

 of Monte Cassino, and was thence removed to the 

 university of Naples. At the age of seventeen, he 

 entered a convent of Dominicans, much against the 

 wishes of his mother, who persevering in her wishes 

 to recover him, the monks, anxious to secure so 

 honourable an addition to their fraternity, determined 

 to send him out of the kingdom to Paris. He was, 

 however, arrested by his two brothers on his way, 

 and, refusing to give up his intention, was shut up in 

 a castle belonging to his father for two years. He 

 at last, however, found means to escape to Naples, 

 and, in the year 1244, was conducted by John, mas- 

 ter of the Teutonic order, to Paris, whence he soon 

 after departed to Cologne. At Cologne, he studied 

 under Albert, an eminent teacher of philosophy, who 

 foresaw his future celebrity. In 1246, he visited 

 Paris, in company with Albert, and, at the age of 

 twenty-four, became a preceptor, at the university of 

 that capital, in dialectics, philosophy, and theology, 

 and acquired the highest reputation. Princes and 

 popes held him in the greatest estimation, and he was 

 invited by St Louis, then reigning in France, to his 

 court and table. On a visit to Rome, Aquinas dis- 

 tinguished himself by a neat repartee : being in a 



