I8J6.] 



THE CIVIL ENGINEER AND ARCHITECT'S JOURNAL. 



35 



The following is a still more remarkable fact, especially when esti- 

 mated by its consequences. — 



At tlie time of coustrurlinR the canals of l!rctaf;ne there was great 

 difficulty in proctiring hydraulic lime. M. Vicat uiidertook the mission 

 of visiting the localities, and almost immediately discovered iu the quarries 

 of Ponpean, near Reon^s, between the beds of rich lime whicli had been 

 worked from time immemorial, a bed of greenish marl known by the 

 name bruletnori-veri, which the limemakcrs rejected. This rejected 

 bed, after the examination of .M. Vicat supplied nut only all the works ol 

 the Vilaine, and the canal of Isle-et-Kaiice, but has become the sole re- 

 source of that part of the kingdom for all hydraulic works. 



Economical Considerations. 



The price of lime almost always forms a considerable item in the cost 

 of masonry. Limes have very dilferent properties which determine the 

 duration of works and the mo(/c of executing tbem. In countries where 

 lime is abundant and of good quality, the buildings last for ages without 

 having required great expenses for their erection. In such districts ha- 

 bitations, even for the poorest classes, may be built with strict regard to 

 healthfulness and preservation from accidents by tire, by the violence of 

 storms, and the destructive elfects of inundations and great rains. It is 

 on account of such useful applicaiions as these that the labours of engi- 

 neers and chemists deserve the attention of the public authorities and the 

 legislature. Let us consider for a moment this phase of the question ; let 

 us seek to value the number of the services which, iu this respect M. 

 Vicat has rendered to his country. 



It was at Paris that the discoveries of M. Vicat first received a power- 

 ful impulse from the influence of M. IJruyere, it is at Paris that we fiud 

 a valuation of the economy effected by these discoveries. 



Before 1818 tlie hydraulic works of the capital were almost all exe- 

 cuted in plaster or with rich lime. Thence arose tlie annual expense of 

 numerous and costly repairs. From 1818, the date of M. Vicat's first 

 publication, recourse was had to hydraulic lime. It is hydraulic lime 

 which gives to new buildmgs an almost infinite durability. 



The same solidity might have been obtained with the lime of Senou- 

 ches ; but tlie lime of .Seuonclios conveyed to Paris costs 80 to 90 francs 

 the cubic metre, while the lime from the quarries from which plaster is 

 obtained, that lime which, before the researches of M. Vicat, was rejected 

 as refuse, costs about 40 francs. This ditfereuce of cost reckoned for 

 37,000 cubic metres of lime, the quantity used iu Paris from lS18 to 

 1841 in the construction of sewers, resei'voirs, canals, &:c. gives a total 

 saving of more than 1,500,000 francs.* 



One of the members of your Commission superintended part of the 

 works of the fortifications round Paris. He has laid before his colleagues 

 detailed tables, from which it is concluded satisfactorily that at Belle- 

 ville alone during the years 18401-2-3-4 a saving of more than half a 

 million [of francs] has been tlie consequence of using certain lime which 

 ■was found on the spot, but which would have been considered of no value 

 before the learned publications of M. Vicat. 



We now proceed to ofl'er some tables, iu which the saving resulting 

 from the labours of the celebrated engineer appear on the grandest 

 scale. 



Sluices and Barrages constructed in France in accordance with the laws 

 of Aug. 5, 1821, and of Aug. 14, 1822. 



* About 60,0001. English, The metre is rather more than 3 feet 8 inches.— £d. 



LARGE BRIDGES OF HEWN STONE, &C. 



To establish a comparison sufficiently exact between the cost of bridges 

 erected on caissons and piles, and of those which, at ihe present day, are 

 erected on a foundation in concrete, it will be necessary to take some unit 

 of comparison which is independent of the number of arches and their size. 

 ^Ve will choose the area of the surface between the parapets for our pur- 

 pose. 



Proceeding thus, it is found for bridges, where it has been possible to 

 substitute the modern method for the ancient that the square metre costs, 

 on Ijie average, 1,312 francs.* 



Now, for bridges erecled under altogether similar circumstances, but 

 on foundations in concrete, the square metre has cost, on the ave- 

 rage 023 francs. The proportion of the expense of the old system to that 

 of (he new, is as 100 to 47. According to this calculation, if a bridge 

 erected on foundations like those of Jena or of Sevres cost, on the ave- 

 rage, 2,000,000 francs [104,000/.] a similar bridge built iu the modern 

 plan would not cost more than 1,222,000 fr. [18,880/.] consequently the 

 saving would be 1,378,000 francs. Since ISIS there have been 19 great 

 bridges built on foundations in concrete, which, therefore, may be reckoned 

 a saving of 20,182,000 francs [1,047,280/]. 



Of bridges of the average size having a span of 15 or 10 metres for 

 each arch the number is about 30. For each, reckoning in proportion 

 there would be a solving of 23.).000 francs, or for the 30 the saving would 

 be 7,050,000 francs [282:000/.]. 



As for bridges of a single arch of 15 to 20 metres span, there have 

 been constructed more than a thousand during the interval of five and 

 twenty years on royal highways and deparlemeut-roads. In each of 

 these the average saving by Ihe substitution for coH'ei' dams of hewn 

 stone with concrete, in the foundations has been 25,000 francs, or for the 

 whole 25,000,000 [1,000,000/.]. 



Siisi'ENSiON Bridges. 



Prior to July, 1843, there were authorised to be constructed 327 sus- 

 pension bridges of one, two, three, or four spans. If we calculate each 

 to have a span of 100 metres [325 feet English], each costing 100,000 

 francs [4,IJ0U/.], deducting from this sum 30,000 francs [1,200/.], the 

 cost of the platform and means of suspension, there remain 70,000 fr. 

 for the founilations and masonry. Experience having showed that for 

 bridges, as for lodis, the expense has been reduced more than one half, 

 there would be grounds for reckoning here a reduction still more consi- 

 derable ; still, we will estimate it at one half, and then the saving will be 

 22,890,000 fr. 



liecapilulation of the Economy effected. 



francs. 



XVcIrs 67.3.10,000 



Barrages or sluice gates .. .. 13,t)00,UOO 



Locks, &c 20,000,000 



Large bridges 2<;.1>2,000 



Common brid{,'e 7,050,000 



Single ?paii bridges JS.oCO.OOD 



Suspension bridges 22,S90,000 



182,072,000 [if7,2S2,880] 



Other constructions in which economy has been eflTected but without 

 sufficient documents to shew the actual amount are, 



1. Wooden or iron bridges, on foundations of masonry. 



2. Bridge of a single arch, of from to 10 metres span. 



3. Marine quays, dikes, basins, &c. 



4. Foundation of public and private buildings in towns. 



5. Military VI'ouks. 



It is important to remark, that we have not taken into account the ques- 

 tion of time. Now, in these matters, time is money, and becomes, finan- 

 cially speaking, a consideration of the highest importance. The new 

 system of foundations allows the execution of works to be done in one or 

 two years that formerly took five or six. There is therefore iu this res- 

 pect also a considerable saving. 



One conclusion springs out of all the preceding evidence — it is that sup- 

 posing the constructive arts such as they were before 1818, the period of 

 the discoveries of M. Vicat, the greater part of the important works in 

 course of execution would have stopped by the considerations of tims 

 and expense. 



If we did not estimate, how much the remuneration demanded 

 will acquire value from the imposing manner in which it is granted, 

 we should have omitted all these sums and the accompanying re- 

 marks. In a purely financial point of view, what are 0,000 fraiics 

 pension beside the colossal economies for which the country is ia- 

 debted to the labours of M. Vicat? 



The AVorks of M. Vicat compared with those of the Ancients 



Certain of the learned profess an admiration, absolute, passionate, for 

 the monuments of antiquity. According to them, the Greeks and Ro- 

 mans had discovered everything in the constructive arts. The solidity 

 of edifices yet remaining show that the moderns are the real disciples. 

 BI. Vicat has simply rt-discuvercd the methods practised in Egypt, at 

 Athens, at Rome, of which the remembrance was lost in the times of 

 barbarism. , 



Although we do not perceive any injury that these reflectio ns Tvill do 



* About H, Os. 6. per square foot. 



5* 



