With regard to the reservoir, it is a large square building to which the aqueduct joins, by several semicircular arches of about 60 feet span, and into which the water from the channel was to flow in a cascade, and thus fill it up to 25 feet in depth. But it was afterwards judged to be unsafe, from the internal pressure being likely to force the walls, and do mischief in the city, which, from being completely commanded by the reservoir might be incalculable The internal dimensions of the cistern are 92 feet 7 inches by 79 feet 10 inches, and 25 feet deep. Four stone piars of eight feet square, rise from the bottom of the cistern, to support the brick vaulting above, which is still unfinished. The floor is finely laid, and the sluices well executed. The view from the summit of this building is superb, presenting every feature of a fine landscape. On the external face of the south side of it, a marble tablet contains the following inscription. Joannes V Lusitanorum Rex Magnificus Civitate Profitens Excipiendis Aquas Populo Manantibus Hanc Molem Struendam Curavit Orbis Miraculum Tanti Nominis Aeternitatis And on a Triumphal Arch adjacent, the following: Joannes V Lusitanorum Rex Justus Pius Aug Felix P. P. Lusitania in Pace Stabilita Viribus Gloria opibus Firmata Imo Prope Victa Natura Perennes Aquas in Urbem invexit Brevi undivigenti Annorum Spatio Immensum opus confecit Optimo Principi Publicæ utilitatis Auctori Hoc Monumentum Pos. S. P. Q.— Anno MDCCXXXVIII The water channels r r (Plate V.) are hollowed out of one stone, and cemented at every joint, with a composition of finely powdered brick, freestone, and limestone, mixed up with oil and turpentine. The channels are 13 inches wide by 11 inches deep, but seldom contain more or less than 7 inches depth of water in summer or winter. The difference of level between the commencement and termination of the aqueduct was not ascertained, but the velocity of the current was 90 feet per minute, and the consequent expenditure 279 English gallons in that period. There are sixteen fountains, each of which is said to yield 11⁄2 almudas* in 75", or 2774 quarts, or 693,5 English gallons, per minute, or 11096 gallons for all the fountains, from which the water must be carried by the galegos, or porters, Eighteen men are constantly employed, whose wages and incidental expenses amount to 700 milrees per month, or about 31541. annually. The annual revenue is ninety millions of reis,* or 25,125l. leaving a disposable sum of 21,9711. These calculations being merely collected from verbal statements, cannot be relied on. * The almuda is about 23 quarts. + Arising from a tax of one rei on every pound of meat sold in the market. The velocity of the stream is the only criterion of authority we have; inaccuracies and mistatements may have unavoidably occurred; but whatever was subjected to measurement, is given with confidence. Thus much for this undertaking. Its merits, its principles, and its utility, may be called in question. In point of magnitude it has few rivals; and the reflecting mind, while it censures its defects, allows its Author to say with the poet, Exegi monumentum ære perennius Quod non imber edax, non Aquilo impotens Possit diruere, aut innumerabilis Annorum series, et fuga temporum. Non omnis moriar, multaque pars mei ART. XII. Report of Mr. Brande's Lectures on Mineralogical Chemistry, delivered in the Theatre of the Royal Institution, in the Spring of 1817. [Continued from page 73.] IRON is a metal so generally diffused throughout nature, that there are comparatively few fossils which can be said to be perfectly free from it. It is confined to no particular formation, or series of rocks, but pervades primary, transition, secondary, and alluvial strata. Water often holds one or more of its saline combinations in solution, and thus forms chalybeate springs; and vegetable and animal bodies afford more or less of it when submitted to the processes of analysis. The proper ores of iron are also very numerous, and it exists in so many combinations with other bodies, that it often becomes very difficult to say what should be regarded as the characteristic ingredient. These considerations alone, render the subject now before me of much interest to the mineralogical and analytic chemist; but when we reflect upon the circumstances connected with it, the history of iron assumes an importance which might justly entitle it to be distinguished as the king of the metals. It is the principal metallic ingredient in those lapideous masses, which in different countries have fallen upon our globe, and which have been termed meteoric stones. Though we really know nothing of the source or origin of these bodies, it has been ascertained upon the most satisfactory and indisputable evidence that they are not of terrestrial formation, and consequently, since men began to think and reason correctly, their visits to our planet have awakened much speculation, and some experimental research. In the first place, it deserves to be remarked, that we have very distinct evidence of the falling of stony bodies from the atmosphere in various countries, and at very remote periods. For, to say nothing of the fabulous trash which encumbers the annals of ancient Rome, or the extended catalogue of wonders flowing from the lively imagination of Oriental writers, such events are recorded in holy writ, and have been set down by the most accredited of the early historians; and although philosophic scepticism long contended against the admission of the fact, it has in modern times received such unanswerable proofs, as to be allowed by all who have candidly considered the evidence, and is only rejected by the really ignorant, or by those who, for the sake of singularity, affect disbelief. The first tolerably accurate narration of the fall of a meteoric stone, relates to that of Ensisheim, near Basle, upon the Rhine. The account which is deposited in the church was thus: A D. 1492, Wednesday, 7 November, there was a loud clap of thunder, and a child saw a stone fall from heaven; it struck into a field of wheat, and did no harm, but made a hole there. The noise it made was heard at Lucerne, Villing, and other places; on the Monday King Maximilian ordered the stone to be brought to the castle, and after having conversed about it with the noblemen, said the people of Ensisheim should hang it up in their church, and his Royal Excellency strictly forbade anybody to take any thing from it. His Excellency however, took two pieces himself, and sent another to Duke Sigismund of Austria. This stone weighed 255 lbs. In 1627, 27th November, the celebrated Gassendi saw a burning stone fall on Mount Vaisir, in Provence; he found it to weigh 59 lbs. In 1672, a stone fell near Verona, weighing 300 lbs. And Lucas, when at Larissa, 1706, describes the falling of a stone, with a loud hissing noise, and smelling of sulphur. In September, 1753, de Lalande witnessed this extraordinary phenomenon, near Pont de Vesli. In 1768, no less than three stones fell in different parts of France. In 1790, there was a shower of stones near Agen, witnessed by M. Darcet, and several other respectable persons. And on the 18th of December, 1795, a stone fell near Major Topham's house in Yorkshire; it was seen by a ploughman and two other persons, who immediately dug it out of the hole it had buried itself in; it weighed 56 lbs. We have various other and equally satisfactory accounts of the same kind. All concur in describing a luminous meteor moving through the air in a more or less oblique direction, attended by a hissing noise, and the fall of stony or semimetallic masses, in a state of ignition. We have however evidence of another kind, amply proving the peculiarities of these bodies. It is, that although they have fallen in very different countries, and at distant periods, when submitted to chemical analysis they all agree in component parts; the metallic particles being composed of nickel and iron; the earthy of silex and mag nesia. Large masses of native iron have been found in different parts of the world, of the history and origin of which nothing very accurate is known. Such are the great block of iron at Elbogen in Bohemia; the large mass discovered by Pallas, weighing 1600 lbs. near Krasnojark in Siberia; that found by Goldberry, in the great desert of Zahra, in Africa; probably also that mentioned by Mr. Barrow, on the banks of the great fish river in Southern Africa; and those noticed by Bruce, Bougainville, Humboldt, and others in America, of enormous magnitude, exceeding 30 tons in weight. That these should be of the same source as the other meteoric stones, seems at first to startle belief; but when they are submitted to analysis, and the iron they contain found alloyed by nickel, it no longer seems credu |