AQUA TOFA'NA. 



AQUEDUCT. 



Another proof must be taken, and the plau then 

 finished with the burnisher, which some use with oil, but other* 

 prefer to use dry, previously filling the whole pUte with powdered 

 white lead, by which it can be seen bow much has been burnished 

 down, according to the quantity of colour left in the plate. 



AQfA TOKA'N A, a poiaonou* fluid invented about the middle of 

 the 17th century by an Italian woman of the name of Tofana. This 

 woman, who resided first at Palermo, and afterwards at Naples, waa 

 on* of the most celebrated of a class of persons known under the name 

 of Secret Poisoners, who in ancient time* were believed to possess the 

 power of destroying life at any stated period, from a few hours to a year ; 

 and who, during the 16th and 17th centuries, were regarded in all the 

 nations of Europe with extraordinary terror. In the year 1669, during 

 the pontificate of AUrrandm- VII., it waa observed at Rome that many 

 young married women became widows, and that many husbands, sus- 

 pected to be not agreeable to their wives, died suddenly. The govern- 

 ment used great vigilance to detect the poisoners. Suspicion at length 

 fell on a society of young wives, whose president appeared to be an old 

 woman, who pretended to foretel future events, and who had often pre- 

 dicted very exactly the death of many persona. By means of a crafty 

 female, their practice* were detected ; the whole society were arrested 

 and put to the torture, and the old woman, whose name waa Spara, 

 with four others, were publicly executed. It appears that Spara, 

 who was a Sicilian, derived her art from Tofana at Palermo, the 

 Utter selling the poison, which hence acquired the name of Aqua delta 

 T-jfa*a, in small glass phials with this inscription, " Manna of St. 

 Nicholas of Barn," and ornamented with the image of the saint. 

 Though this infamous woman lived to on advanced age, she was at 

 length dragged from a monastery, in which she had taken refuge, and 

 put to the torture. She confessed that she had been instrumental to 

 the death of no leas than 600 persons. 



The dose of her poison was from four to six drops ; yet though in 

 Uu* state of concentration it* nature could not be detected, it was sub- 

 sequently discovered to consist of a solution of arsenic ; but so little 

 was that age acquainted with the art of chemical analysis, that they 

 had no mean* of detecting a solution of arsenic so highly concentrated 

 that from four to six drop* was a mortal dose ; whereas, at present, 

 even when arsenic ha* been dissolved in the stomach and mixed with 

 vegetable and animal fluid*, it may be reduced to it* metallic form, and 

 made to exhibit all the physical properties of the metal to the naked eye 

 with a* great distinctness as in any quantity, however large, ichea only 

 Ike tteentietk part of a grain hat been procured. Modern chemistry 

 therefore ha* deprived the poisoner by arsenic of all chance of escape by 

 concealing or disguising the poison he administers. 



AQUJSDUCT, or AQUEDUCT (aqua Jurlut), the channel or pas 

 sage for conducting water ; of late yean, however, the word conduit 

 has been more commonly used to express the generic idea of a con- 

 ducting paaasge, whilst the word aqueduct ha* been applied specifically 

 to the clans of structures which perhaps it would be more correct to call 

 AO.I n>rcT BRIDGES. As, however, this specific signification of the word 

 has some advantage*, it will be hereafter adopted in this Cyclopaedia, 

 and the following notice of Aqueduct* will be devoted exclusively to 

 an investigation of the practice of ancient and modern engineers, in 

 the construction of bridges for the purpose of conveying streams of 

 water above the surface of the ground from one comparatively high 

 point to another. The Uws of the flow of water in conduit* (whether 

 of masonry, open or covered, or of earthwork, wherein the water flows 

 simply by the effect of gravitation ; or of closed pipes, wherein the 

 flow U effected by the pressure at the entry), will be discussed under 

 the articles COHDCIT and WATER I'II-ES ; whilst the investigation of 

 the contrivances for the conveyance of water for the supply of town 

 populations will be reserved to the article WATER SUPPLY. 



It does not appear that either the Assyrians, or the Egyptians, 

 execute.! any important works of the kind under consideration ; for 

 although unquestionably the systems of irrigation they adopted, and 



orial representations in the sepulchral monument* of the 

 would lead us to believe that they were acquainted with 



z principles with respect to the flow of water, and were even 

 aware of the effect* of hydrostatic pressure, no remains of the aqueduct* 

 executed during the 



... . 



be periods of the independent existence of thn 

 U of those countries have survived to our days. In 



Greece, sad in Asia Minor, there are some remains of aqueduct* ; but 

 the style of their construction would rather lead to the belief that they 

 were erected sutMquently to the Roman conquest; and, indeed, their 

 outlines more closely approximate to the principles of Latin, than 

 they do to those of Hellenic, art The most authentic example uf n 

 Greek aqueduct is supposed to be the one described and figured by 

 Mr. Q. Rennie, hi the Proceedings of the Institution of Civil Engineers, 

 Jan. Iflth, ISIS; md it is the more interesting from the fact of it* 

 illustrating the practical application of the principle of the reversed 

 syphon at a very early period in the history of art. The valley near 

 Patera on the coast of Lycia, where this aqueduct wu erected, U about 

 MO feet deep, and 200 feet across; and In it a wall uf loose rubble 

 masonry, at the bottom of which is left a small rough arch for the 

 passag.) of the stream flowing in the ravine, ha* been formed termi- 

 nating with a aeries of wrought stone block*, well cramped together, 

 closely jointed, and bedded in cement. The*; blocks are laid in a 

 curved line, with it* chord on the upper side ; and they were perforated 



with a circular hole 13 inohea in diameter. It U said that at Syracuse 

 than are also remains of aqueduct* of Greek construction, and that 

 near Antioch an important work of this description waa erected during 

 the reigns of the Svleucidaj. But the mode of arching introdn. 

 the Utter work U so decidedly in the ty ! >* tin- Koiiian engineer!, 

 that it U hardly possible to attribute thin monument to any one else 

 than to the masters of the ancient world ; jnxt as it is necessary for 

 the same reason to attribute to them the construction of the aqueduct 

 t \l,r. 



The Roman government appears, at a very early period of it* 

 existence, to have felt the necessity for supplying Urge quantities of 

 pure water to the inhabitant* of the great centrea of population sub- 

 mitted to it* sway ; and naturally it executed a series of important 

 works for the supply of the Eternal City itnelf. Rome, in fact, waa 

 built on the bantu of the Tibur, a stream so turbid as to merit and 

 receive the name of the ' FUvum Tibrim ; ' and the quantity of* water 

 obtainable from wells sunk in the alluvial formations of the valley waa 

 soon found to be insufficient for the continually increasing population. 

 About the year 812 B.C., then, Appiua Claudius erected the first 

 conduit through which the waters, afterwards known as the Aquto 

 Appiamo, were led into Rome. From that period to the close of the 

 republican era, several other great works of this descriptioi: 

 erected ; such aa the Anio Vetua about 278 B.C. ; the Aqua Marcia 

 about 146 B.C. ; the Aqua Tepula about 127 B.C.; this last conduit 

 was subsequently increased in importance by the addition of the Aqua 

 Julia, in the year 35 B.C. ; and in the very earliest days of the empire, 

 Agrippa increased the supply of water in the eternal city by leading 

 into it the Aquas Virgo, Alsietina, and Augusta. At later periods the 

 Aqucc Claudia, Anio Vetus, and Alexandria were conducted to Rome, 

 and thus added to the already copious supply of water it possessed. 

 From the local conditions of the city, and of it* neighbourhood, the 

 streams thus diverted were forcedly brought from a great distance ; 

 and they arrived in the alluvial plain of the Tibur at a considerable 

 elevation. It seems that the total lengths of the various conduits 

 formed previously to the end of the first century of our era, was about 

 456,987 yards, of which' 4930 yards were supported on a solid sub- 

 structure, and not lees than 53,421 yards were carried by aqueducts, 

 in the limited sense of the word now adopted, which were frequently 

 from 80 to 100 feet in height. In the province* also the Roman 

 engineers erected numerous important works of the game description, 

 amongst which may be cited the aqueduct* near Nlmes, Mete, Luynes, 

 Frejus, Trevex, Arceuil, Segovia, Tarragona, Evora, Merida, Carthage, 

 Constantino, Tunis, Cairo, &c. ; whilst at a later period of their rule 

 they erected some ruder, but still colossal, aqueduct* for the supply of 

 Constantinople. 



The practice of the Roman engineers in the construction of aque- 

 ducts, appears to have been to avoid Urge openings when the length 

 between the sides of the valley was considerable. They appear to have 

 been induced to adopt thin principle, on account partly of their desire 

 to avoid expense in foundation works, and partly on account of the 

 dillieulty they must have encountered in framing large centrea such as 

 should be able to carry the weight of an arch of considerable span, 

 from the high price and the rarity of wrought iron. Whatever were 

 their determining motives, the ruling dimensions they adopt**! wen 1 . 

 for the openings, when dressed stone or ashlar was used, between 24 

 and 50 feet ; though in the case of the Pont du Gard, the span of the 

 largest arch is 80 feet ; and in some of their road bridges even greater 

 openings were admitted, as in the bridge of Alcantara, which has a 

 span of 101 feet, and in that of Narni, which has a span of 139 feet. 

 When the material employed was a small rubble stone, with ashlar 

 bond courses, the spans usually varied from 18 to 3<i iY.-t : and when 

 rubble or brick-work alone were used, the spans were limited to 24 

 feet, a* a maximum, and were usually made from 15 to 18 feet. The 

 width of the aqueduct varies from J to J of the openings, and (lie 

 thickness of the piers from J to J of the span, though there are in.-.ny 

 examples in which they are made equal to the Utter. When the 

 height was considerable the aqueducts were built in tiers; but until 

 the clear height under the key-stone attained 80 feet, tl,. I 

 engineers do not appear to have hesitated in executing such works 

 .!y one range of arches; when that height became from 90 to 

 160 feet, it was customary to construct two ranges of archi- 

 when it became from 180 to 250 feet three ranges were imr.-di,, . .1. 

 Their engineer* seem also to have studied carefully the l.-mx <if per- 

 spective in designing these structures; for tin- proportions of the 

 respective ranges of arches are almost always such as to produce the 

 moet agreeable effect upon the eye. The height from the ground to 

 the underside of the first tier was usually made equal to 2) times the 

 opening of the arches; the distance from the underside of the key to 

 the top of the first horizontal line was made about 4 the opening ; the 

 second row of arches was made about t less in height than the first, and 

 the third row J less than the second. In the erection of the great 

 modern aqueduct of Caserta, Vanvitclli neglected to observe these 

 Uws of perspective, and he mode the upjK-r tier of arches loftier tli.in 

 either of those beneath it ; thus entirely marring the effect of what 

 would otherwise have been a very fine monument. 



But though the Roman engineers thus habitually resorted to the 



iction of aqueducts when they were compelled to cross deep 



valleys, they unquestionably did so from motives of economy, or from 



