Chap. VI.
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The plan, section, and elevation explain its character and proportion : it is executed witha hard and durable stone, in a most admirable manner. Its length is 212 feet, and width128 feet. The roof is formed entirely of iron and copper, and the court or area occupiedby the merchants is 116 feet long and 76 feet broad, and it is calculated will contain 2000
persons. The agens de change, or brokers, have a portion railed ofT for their especial ac-commodation ; and around the great court are the tribunal and chamber of commerce, thecourt of bankruptcy, and several other halls for the convenience of the merchants and others,and the cost was upwards of 300,000/. sterling.
The exchange marks the importance of a city, and should always be erected in the midstof the most thronged part, and rendered capable of receiving not only the native, but allforeign merchants who attend : in its architecture we expect to find that the best talent thecountry can produce has been employed, and certainly in this example we are not disap-pointed.
Artesian wells have long existed in Italy , in Austria , in the Crimea , Siberia , Sahara,Palmyra, Balhec, Tyre, and Egypt ; their modern name arises from their having been im-memorially used in Artois, one of the departments in France . Belidor mentions one in1749 at the monastery of St. Andre, near to Aire, and in the ancient convent of theChartreux, at Lillier, in the same neighbourhood, is another more than 700 years old.
About the year 1824, M. Peligot, one of the superintendents of the hospitals at Paris ,suggested the idea of sinking a well upon the Artesian principle, and workmen were sentfrom Artois for the purpose ; whilst this was being effected, M. Mulot, a smith, became in-terested in the operation, and turned his attention to the subject; he was consequentlyemployed by the Marchioness de Groslier to sink one at Epinay ; success attended hisefforts, and he was nominated to attempt one at Grenelle. The primitive soils, accordingto M. Arago, are but rarely stratified, or are found in regular beds. The fissures in graniticrocks, the crevices separating the contiguous masses, have but little width or depth, and donot frequently communicate with each other; in such soils the waters of filtration have butlimited outlets, each film or thread terminating its course alone, without receiving anyincrease from others in their descent. The springs being numerous in the neighbourhood,it was not thought probable that any vast quantity of water could be obtained, as the wholeof the rain penetrating the earth was supposed to pass off through various openings in thesides of the hills.
The secondary soils, which are composed of a variety of rocks, in general take the formof immense reservoirs or basins, the centre being considerably depressed, or the extremeboundaries of it greatly elevated: within this basin hills, and often mountains, arise,apparently destroying its original character. The stratification of the secondary formationis in regular beds, some of which are of enormous thickness, composed of sand or grit, andvery permeable; these permeable beds, as they rise towards the extremities of the basin, be-come bare on the sides of the mountains and hills. The rain water which falls on the earth,after penetrating it, forms one continued sheet, which pursues its course with great rapiditywhen the beds have a great declivity, and, reaching the lowest point, is accumulated in vastquantities. One chalky or calcareous stratum, which is furrowed out in all directions, andparticularly in the upper portion, allows the pluvial water to pass with great facility, andalso to circulate through the mass to a great depth: and in this peculiar stratum the wellsboth of Grenelle and Rouen have been bored.
The tertiary soils are stratified, and composed of many beds placed over each other, and
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