AQUEDUCT. 



ARA. 



453 



dread of deposition in the pipes, rather than from ignorance of the 

 laws of hydrostatics. Gauthey gives a description of a lead pipe 

 dredged from the bed of the Rhone, which had evidently formed part 

 of a reversed syphon in the course of the conduit of Aries ; but the 

 most remarkable instance of the use of such reversed syphons by the 

 Romans, in connection, it is to be observed, with ordinary aqueducts, 

 is the one described in Delorme's ' Recherches sur les Antiquite's de 

 Lyon.' In this case the water brought from the Mount Pila is carried 

 across several valleys, by means of thirteen aqueducts and three syphons ; 

 the first of which syphons, between the hills of Soncieu and Chaponest, 

 is laid in a valley about 2600 feet across, and 217 feet deep ; the second 

 between Baunan and St. Foy, in a valley 3458 feet wide, and 325 feet 

 deep; and the third between St. Trance and the gate of Trion. A 

 description of the Soncieu syphon is added ; but it may be important 

 here to observe, that a great deal of the interest attaching to this work 

 arises from the singular illustration it affords of the state of the metal- 

 lurgic arts amongst the Romans. 



The water is admitted, on the upper side, into a reservoir of masonry, 

 in the walls of which are inserted, at about 10 inches from the floor, 

 nine lead pipes, 8} inches diameter and li inches thick. These pipes 

 are carried down the side of the valley on a species of substructure, 

 arched in some places, so as to preserve a regular inclination ; they are 

 of the same.diameter, as at the commencement, for a distance of 81 feet, 

 and they then bifurcate into pipes of 6 inches diameter each. The 

 eighteen smaller pipes are continued to the bottom of the syphon ; but 

 instead of descending quite to the lowest part of the valley, they are 

 carried across an irregular depression of the latter on an aqueduct of 

 about SO feet maximum height ; so that in fact the descending limb of 

 the syphon is only about 164 feet in vertical height, and the descending 

 limb is about 142 feet 2 inches. Midway in the ascending limb, the 

 two 6-inch pipes are re-united into 9-inch ones, and the latter pour the 

 waters they convey into a small reservoir corresponding with the one 

 on the descending side. The Baunan syphon was deeper than the 

 Chaponest one, in fact, the dip of the descending limb was 282 feet ; 

 and therefore the diameter of the pipes at starting was smaller. The 

 fit. Trance syphon was of considerably less importance than either of 

 those above mentioned. Count Caylus, who examined the remains of 

 these pipes very carefully, states that they contained so eimr 

 quantity of lead, that, even in his day, it would have been worth at 

 least 500,000<. : what it must have cost in the time of Claudius Ca.-s.ir 

 it would be impossible to say. The engineers of the Ponte dell' Arcate, 

 on the conduit which supplies Genoa with water, adopted, in 1782, 

 precisely the same system of syphon aqueduct thus described as 

 having been used by the Roman engineers at Lyon, substituting 

 cast iron however for lead; and a modification of the same system 

 was even applied by the engineers of the Croton Waterworks, New 

 York. 



Amongst the most important aqueducta erected since the fall of the 

 u empire may be cited the aqueduct of Spoleto, said, though, 

 without reason, to have been built by Theodoric the Goth. It is how- 

 ever unquestionably of great antiquity ; and perhaps it merits more 

 attention than it hitherto has received, if it were only for the sake of 

 correcting the errors printed in all works upon architecture with respect 

 to it. Thus, in all those works, the height of the Spoleto aqueduct is 

 said to be not less than 420 feet ; but from recent measurements it 

 would appear that the real height does not exceed, even if it attain, 

 240 feet. There is a remarkable aqueduct of the Renaissance period 

 near Pavia ; and at C'aserta is a very lofty one, before mentioned as 

 having been constructed by Vanvitclli : the latter aqueduct is about 

 2000 feet long and 200 feet high in the deepest part of the valley. At 

 Lisbon there is an aqueduct, erected by Mauoel da Maya, a Portuguese 

 engineer, about 1738, of about 2600 feet in length and 231 feet in 

 height ; and about the year 1680 Vauban and Lahire had commenced 

 the gigantic ruin which was intended to have carried the Eure to Ver- 

 sailles. This work was designed to have been of a total length of 

 3| miles nearly, and of a height of 234 feet. The aqueduct of Mont- 

 pellier is about 2300 feet long and 92 feet high, in round numbers ; 

 whilst (the Roquefavour aqueduct, lately erected near Marseille, is 

 1312 feet long by not less than 282 feet in height. In England there 

 are some large canal aqueducts, such as the Chirk and Pont y Cyssylte 

 bridges, of cast iron, erected by Telf ord, and the Lune aqueduct, erected 

 by Reunie ; and of late years some remarkable works of the same 

 description have been erected in France and in Italy, either for the 

 canal or the irrigation works of those countries ; but all these works 

 sink into insignificance when compared with the aqueducts recently 

 erected by the engineers connected with the Irrigation departments of 

 our Indian empire. The great Solani aqueduct, upon the Ganges 

 u, for instance, of about 1050 feet in length, with an average 

 height of 51 feet; but aa the area of the water-way in the Solani aque- 

 duct in aa nearly as may be 80 times as much as that of the aqueduct 

 of the Pont du (jard, it would be impossible to draw anything like a 

 oompoiM between the two. 



It may be necessary to add, that English engineers have almost 

 entirely abandoned the use of aqueducts for town supplies, and that 

 they have substituted for those costly monuments the simpler system 

 of laying reversed syphons in the valleys through which they have to 

 carry a water supply. In the cases of the Liverpool, Manchester, and 

 Glasgow water-worki, some remarkable illustrations of this practice 



may be observed, which will be noticed hereafter under the head 

 SYPHON, REVERSED. 



A'QUILA (the Eagle), a constellation situated above, so as to rest 

 on, Capricornus and Aquarius. It may be readily found by means of 

 the head of Draco and the bright star a Lyrse, since a line passes 

 between /3 and y Draconis, and through a Lyrso, passes through a bright 

 star of the first magnitude, o Aquilae, cutting also two stars of the third 

 magnitude, ft and y, situated directly above and below a. This constel- 

 lation is on the meridian at 8 o'clock P.M. in the middle of September, 

 at about 40 of elevation. The following is an analysis of the number 

 of stars visible to the naked eye in this constellation, arranged in the 

 order of their respective magnitudes : 



Magnitude. 

 1-5 

 3 



8-5 



4- . 

 4-5 

 5 



5-5 

 6- 



Number of Stars. 



. 1 

 . . 3 



. 4 

 . . 2 



. 1 

 . . 10 



. 12 

 . . 28 



Total number . . 61 

 The stars down to the 4th magnitude inclusive are thus designated :- 



No. in Catalogue 

 No. in Catalogue of British 

 Character. of Flamsteed. Association. 



c 

 \ 







B 



13 

 16 

 17 



30 

 39 

 58 

 53 

 55 

 66 

 fio 



6487 

 6526 

 6528 

 6646 

 6713 

 6772 

 6802 

 6811 

 6833 

 6934 



Magnitude. 

 3-5 

 3 

 3 



3-6 

 4 

 3 



1-5 

 4 



3-5 

 3-5 



In the Greek mythology, this constellation represents the eagle of 

 Jupiter. According to some, it is the bird which wis the tormentor of 

 Prometheus. M. Dupuis conjectures, but with very little probability, 

 that the name was given when Aquila was near the summer solstice, 

 and that the bird of highest flight was chosen to express the greatest 

 elevation of the sun. 



The constellation Antinous is usually considered as a part of Aquila, 

 and is treated as such in catalogues. It is represented as a boy in the 

 grasp of the eagle, and its principal stars are n, 9, t, K, and \, in the 

 above catalogue. It is said to have been placed in the heavens by the 

 order of the Emperor Hadrian, in memory of a favourite of that name, 

 who is generally supposed to have perished in the Nile, A.D. 131. 

 Others have supposed it to refer to the fabulous history of Ganymede, 

 who was carried to heaven by the eagle of Jupiter ; but this is rendered 

 unlikely by the silence of Ptolemy, who, though he speaks of the group 

 of stars in question, does not call them the constellation Antinous, but 

 simply "unformed stars, among which is Antinous." Had the two 

 figures originally contained any reference to the mythology above 

 alluded to, it is most probable that the constellation would have been 

 regularly distinguished long before the time of Ptolemy. 



ARA (the Altar), a southern constellation, not visible in our latitude. 

 It is situated near Lupus, above Pavo and Triangulum Australe, in such 

 manner that the Centaur appears to be placing the wolf upon the altar. 

 One mythological account explains it as the altar upon which Chiron 

 sacrificed a wolf; another, as an altar constructed by Vulcan, upon 

 which the gods swore fidelity to each other during the war against the 

 Titans. 



The following is a classified enumeration of the stars visible to the 

 naked eye in this constellation : 



Magnitude. 

 3 



3-5 

 4 



6-5 

 6 



Number of Stars. 



. 3 

 . . 1 



. 3 

 . . 4 



. 48 



Total number of stars . . 59 

 Subjoined are the designations of the principal stars : 



No. in Catalogue 

 No. in Catalogue of British 



Character. of Lacaille. Association. Magnitude. 



9 7535 5683 4 



a 7301 6697 3 



7271 5850 4 



7237 5852 3 



7 7233 6877 3 



' 7050 5899 4 



C 7034 6105 8J 



