240 



THE CIVIL ENGINEER AND ARCHITECT'S JOURNAL. 



[AvfilST, 



Tlie calcareous stones when first extracted are certainly in a 

 very different state to that in which they appear after liisinij the 

 quarry damp, to use the expression of tlie quarrymen. 1 suspect 

 tliat they exist in tlie quarry only as a suh-carlmnate of lime; at 

 any rate, it is certain tliat they are hydro-carbonates. In cither 

 case the lime is, comparatively speaking, free to enter into new 

 i-unihinations. If sea water he introduced, the magnesia enters 

 into combination witli tlie lime, the more readily if carbonic acid 

 be present, giving rise to the formation of a niagnesian carbonate 

 of lime. The sulphuric acid gas also enters into combination with 

 the lime, giving rise to the formation of sulpliate o<' lime. These 

 combinations take place with the commencement of a confused 

 crystallization, tlie mass is disintegrated, and falls to powder. 



Practically, at Paris, where from the nature of the subsoil it is 

 expensive to form cellars, and where the bulk of the houses are 

 huilt u))on the ground, without deep foundations, where the land 

 is all freehold, building leases are unknown, and consequently 

 where the interest of the (iroprietors is evidently to obtain the 

 greatest number of dwellings upon the least luissible surface, and 

 the houses, therefore, are generally from six to seven stories high, 

 the lower parts of the houses are built of the roche stone, towards 

 the street and up to the first floor; from thence two stories are 

 carried up in la pierre franche; and the remainder is executed in 

 lambourde. The party walls are mostly executed of moellon, or 

 small coursed stones, of similar natures to the corresponding parts 

 of the facade. The back walls and partitions are of wood, filled 

 in with light rubble, and plastered. Such construction is about as 

 had as can be: the front wall, built of cai-efully-squared ashlar, 

 sinks very little. The party walls, of rubble and plaster, not only 

 sink more than the front, hut, from the fact that the plaster in 

 setting expands, it becomes necessary to build these walls totally 

 independent of one another. The back walls, of wood framework, 

 shrink still more. It is therefore almost impossible, in the new 

 quarters of Paris, where this style prevails, to find a house which 

 is not disfigured in all directions with cracks and settlements of 

 every kind and size imaginable. 



The mode of using the stone is, however, logical, and merits 

 imitation. The harder and less hygrometric stones are placed at 

 the bottom, as being the most fit to resist the crushing weight and 

 the capillary action of the stone upon the humidity of the soil. 

 The finer grained stones are employed at the heights destined ! 

 usually to he ornamented; the lighter and more perishable stones ; 

 are used above, where they load the foundations less than the 

 others would do, and where they meet with the atmospheric condi- 

 tions the most adapted to their own preservation. 



In Ilouen, the Chin-ence stone, or that of Vernon, are used in 

 the situations where the roche is used at Paris; the upper parts I 

 are of the softer stones. At Havre the same rule is observed: the 

 Cherence, Caumont, Ranville, or granite, are used in all cases 

 where there is danger to be feared from humidity; the Caen stone , 

 is only used in the upper works. Wherever I have seen the Au- [ 

 bigny stone used, it has decayed rapidly. Indeed, the French ar- 

 chitects do not much advocate its use externally. 



The value of the building materials extracted in 1815 was, for 

 the departments before cited, as follows: — 



besides the value of the slates, quoted previously. 



3rd. IVie Gi/picons Sloneit. — These stones, from their soft and 

 friable nature, and the facility with which tliey decompose in the 

 atmosphere, are not allowed to be used as building materials in 

 Paris. Sometimes enclosure walls are built of them, employed as 

 moellon. Tlie principal use is in the fabrication of plaster. 



The chemical nature of these stones as found at Montmartre, 

 Belleville, Charonne, Menilmontant, le Calvaire, Triel, and Meu- 

 lan, is, according to Fourcroy, 32 parts of oxide of calcium, 1-6 

 parts of sulphuric acid, and 22 parts of water. They differ from 

 the gypsums of other countries, in the large quantities of lime 

 they contain, which gives them greater powers of resistance to the 

 action of the moisture of the atmosphere. The operation of burn- 

 ing consists simply in driving off' the water of crystallisation. In 

 this state the plaster has a remarkable avidity for water, and im- 

 mediately that any is presented it absorbs it, and crystallises 

 around the bodies in its immediate vicinity. I noticed previously 

 the singular fact of the swelling of the plaster during this pro- 

 cess; it is one that requires great attention in the employ of the 



material. Another fact worthy of notice is cited by Rondelet — 

 namely, that two bricks set together with plaster adhere with one- 

 tiiird more energy than briiks set with lime during the first month; 

 but that afterwards their adhesion diminishes, whereas that of the 

 bricks and mortar increases almost indefinitely. 



4th and .5th. TIte SUiceonx Stoiif.s, ^r. — They comprehend the 

 gres, flint nodules, the meuleres, the granites, porphyries, and the 

 basalts. 



The gres is a species of imperfect sandstone formation, at least 

 as it occurs near Paris, and in the department of the Lower Seine. 

 It is composed of a fine sand of a whitish tinge, cemented together 

 by a silicious cement. Generally s]>eaking it occurs in detached 

 nodules, named "rognons;" sometimes it occurs in layers of differ- 

 ent thicknesses. The quarrymen observe that the lower they de- 

 scend the softer the gres becomes, and that the harder nature of 

 stone is the most easy to quarry in regular forms. It has no defi- 

 nite planes of stratification or crystallization, and is tlierefore 

 easily worked into any shape I'cquired. The streets of nearly all 

 the towns between Paris and the sea-board are paved with these 

 tertiary gres, %vhich occur in isolated patches along the whole 

 course of the river. At Havre, of late, the red sandstone of JVIav, 

 near Caen, a member of the Cambrian system, has been employed 

 instead thereof, with remarkable success. The usual size of the 

 paving stones is 9 inches square; but some of the last works of 

 this kind have been executed with nai-rower stones, about 4 inches 

 wide. 



The flint nodules are sometimes used for rough rubble masonry. 

 They occur in chalk and in the gravels overlying the tertiary for- 

 mations. 



The meuliere is a species of quartzose concretion, with numerous 

 small holes. It is met with in two forms; one which occurs in 

 masses sufficiently large to form millstones of one piece; the other 

 in detached nodules scattered over the country. The principal 

 quarries of the first, for the supply of the Paris market, are at 

 Slontmirail (Marne) and la Ferte sous Jonarre (Seine et Alarne.) 

 The second sort are found nearer Paris, and in the department de 

 I'Eure. 



As the meuliere is excessively hard, and resists all external 

 action in the highest degree, it is much used by engineers and ar- 

 chitects in situations where those qualities are required. The for- 

 tifications of Paris and of the detached forts are faced with it. 

 Many of the works of the Canaux St. Martin, St. Denis, and de 

 rOurc, the sewers of Paris, and the abattoirs also, are faced with 

 the meuliere; for all these works it is admirably adapted. One 

 species is, however, to be avoided, — "la caillasse;" its surfaces are 

 so perfectly even that they offer no key to the mortar. 



The granites, a description of which would here be unnecessary, 

 are only used in Paris, and the other towns in the interior, as bor- 

 ders for the footpaths, and occasionally as flagging. That used 

 in Paris is mostly extracted at the island of Cbaussey, and is of a 

 nature closely resembling the best Devonshire granites. The 

 plinths of the columns of the Law Institution in Chancery-lane'^ 

 are of this granite, and may give a correct idea of its nature. 

 The enormous cost of the granite, owing to the land carriage, 

 must at all times limit its use in the interior. At Havre, however, 

 and at Honfleur, it is much used in th^ different docks, and the 

 fortifications towards the river are entirely faced with it. 



The porphyries are very little used, nor do they occur abun- 

 dantly in any position suitable to their being worked for the Paris 

 market. The basalts also are rare, at least for practical building 

 use. They are, however, occasionally used for flagging, as in the 

 Rues de la Paix, de Richelieu, &c. 



II. Bricks and Tiles. — In Paris, the use of bricks is entirely 

 confined to carrying up the flues, and turning the trimmers to the 

 hearths. The best that are emjiloyed are the bricks made in the 

 department of TYoiine, known under the name of the "Briipie de 

 Bougogne;" it is 1 foot long, 4 inches wide, by rather more than 

 2 inches thick. It is burnt to a very high degree. The colour is 

 a pale rose, leaning towai'ds the violet. The thousand weigh 

 about 2^ tons. Rondelet found that the force necessary to crush 

 them varied between 73 lb. and HO lb. per centimetre square. 



The bricks made at Montereau are very nearly as good as the 

 bricpies de Bourgogne; they are of the same size and colour; 

 resist nearly as well. The thousand only weighs 2 tons ^ cwt. 



The composition of the Montereau clay is as follows: — 



Siit-x, per tt'iit ()44 



Alumina U'24ti 



Ala^ne^ii *. 



Oxide ul il'Oll trace 



Water lOH 



0-990 



* That is to say, of the columos of the portico. 



