THE CIVIL ENGINEER AND ARCHITECT'S JOURNAL. [February, 



36 



to the labors of M. Vicat-although the discovery of lost truth seems to 

 «« a together similar to the discovery of a new truth-your Comm.ssioQ 

 hasdevoted it elf to a n,inute examination of the pretended snpenorUy 

 nf the ancients over the „>oderns in the art of h.nldmg. A e l>uve exa- 

 mined moreover, whether this superiority can he main.a.ned on reference 

 To ?he progress due to the discoveries of our illustrious engmeer. 



"So^ie of the Roman mortars have lasted eighteen centunes. A great 

 number of modern buddings are in a deplorable conuit.on ! 



Jhs comparison is essentially erroneous. To give .t any value ve 

 must draw a parallel between none but the greatest monuments of the 

 twoepo^h^- The results will then be very different to those on wh.ch 

 fhp learned support their position. . . , 



The Ramparts of the ISastille were of extreme solidity even in the 

 centre ofThe masonry. It was necessary to use gunpowder to des roy 

 them Gu powder Ls also found necessary a few y^^- »g» '» ""''-y 

 at A-cn the ruins of a bridge built about the year 1200. M J -c, 

 h mself ascertained that the mortar of the bridge of Valentre, built at 

 Cahors in HOOrsurpassed in hardness that of the ancient theatre, of 

 which the ruins are seen in that town. ,. . „ . r ,i,o 



Ancient architects, like modern, built according to the nature of the 

 materials atUieir disposal, and also according to financial exigencies, 

 either edifices whidiwei; indestructible, or with the same oxter.or 

 forms temples, palaces, and houses, without solidity. The construct.ons 

 oftTelitter clas rapidly disappeared. The others a^one have resisted 

 the ravages of time and -fhe violence of the seasons. The blm; ladnnrers 

 of by 'one age have they forgotten the words of Piny, " The cause 

 from«hichaaionieso many buildings fall is the bad quality o, the ce- 



"Tf'asit is pretended, the Romans knew certain methods of preparing 

 good mor ta we ought to find this substance in all their pu M.c nionu- 

 ments with qualities -dmost identical. Now this is not even the case in 

 ron°pari,.g dillerent parts of tlie same edifice. The Commission have le- 

 na ked n many pub ications of M. Vicat's experiments which throw great 

 Stonthi"subject; those, for instance made with mortar taken <ro- 

 ditlerent points of the bridge of Card; these experiments give resistances 

 varvinn- in the proportion of one to tUree. , , , „i, ,. 



Those who devote themselves to these cotnparisons should remember 

 that time acts unceasingly in foundations on the hardnessof moita Ihe 

 mode of action by which this conglomerate hardens-acqiures adhesue- 

 r^_is still a matter of controversy among the learned. But no one can 

 deny that tliere are circumstances under which it is impossible foi this 

 mysterious action to continue for a long series of ages. , , „f ^^ 



It would seem forgotten, .that in considering the knowledge of ce- 

 ments in the art of building, we are not reduced to simple c«"J«^ "[^s^ 

 Vitruvius, contemporai-y and architect of Augustus has left a detailed 

 account of the precepts in use among the builders of Greece and Ron 

 These precepts are far from justifying our unreserved admiration of the 



'^"Tlie'ancients were not in possession of any exact notion concerning the 

 cftemical modification that calcareous stone undergoes id the kdn, a mo- 

 dification by which its friability is so much increased. Neither d,d they 

 know anything of the kind of action which restores to the disintegrated 

 molecules of this stone converted into lime, the adhesion and hardness of 

 Xh they had been deprived by heat. Tlie eirorts of Vitruvius to give 

 a plausible explanation were ineffectual. The same was the case unt 1 

 the chemical discoveries of Black respecting carbonic acid, with the a - 

 tempts of the most illustrious successors of Vitruvius, Scamozzy, 1 hili- 

 bert Delornie, Perrault, &c. j .u i „ .i,„t 



One sin-le word will disabuse all those who persuade themselves tliat 

 the theoretic errors of these great architects are of no consequence lake 

 the instance of Philibert Uelorme: to arrive at a maximum of solidity in 

 edifices, he thought it necessary that the lime should be taken from the 

 same bed of limestone as the materials of the masonry. This direction, it 

 it had been followed out, would have involved an enormous increase of 



^'^BuUders who regulated the choice of their lime by the colour of the 

 rock from which it is obtained ; who were not acquainted with any na- 

 tural hydraulic lime: who were lavish in mixing with their lime brokeri 

 pottery and brick rubbish, cannot, without great injustice, be compared 

 with modern constructors. Putting aside the excellent observations on 

 the properties of natural fozzolanas, on the possibdity of using this mate- 

 rial to make enormous artificial blocks to be sunk in the sea we find that 

 the Romans have taught us nothing essential in the art of building. 



For the rest, every attempt to exalt the merit of the ancient in the con- 

 structive arts only redounds to the merit of I\I. Vicat. The best mortar 

 extracted from Roman monuments has, after two thousand years of anti- 

 quity, a hardness precisely equal to that which M. Vicat obtained with 

 sood limes in the short period of a year or eighteen months. In applying 

 the comparison to average resistances, the advantage greatly preponde- 

 rates for the modern mortar. 



Opinions of Chemists and Builders on the Labours of M. Vicat. 

 The importance of M. Vicat's discoveries is palpable. For about a 

 tiuarterof a century all builders have taken advantage of them : now in 

 such matter, it must be readily understood that it must rest with the ac ual 

 practitioner to pronounce a definitive judgment Nevertheless, not o 

 L-'lect any kind of information, the Commission have thought it right to 

 gather the opinions of chemists and engineers, who are occupied, with the 



greatest success, in the application of science to the arts. In this examina- 

 tion we have met with the most flattering recognitions of the labours ot 

 the celebrated engineer; no one appears to have contested their novelty. 



Is the first memoir of M. Vicat on the production of artificial hydraulic 

 lime presented to the Academy of Sciences? That learned body decide 

 on the motion of MM. de Prony, Girard, and Gay-Lussac, that the me- 

 moir shall appear in the celebrated collection entitled Receud dcs Sarants 

 etran'rers. To this mark of approbation, the greatest that academic com- 

 missions ever give, was soon added a proof of esteem sought for through- 

 out the world ; the Academy named M. Vicat one of its correspondents. 



The Council of Bridges and Highways, called upon at the commence- 

 ment of Ibis, to declare its opinion on the artificial lurmation of hydraulic 

 lime, declare, by their organ, the accurate and skilful M. Bruyere, " that 

 the advanta-es t.f the new method were innumerable, that they dispensed 

 with the cosily employment of real pozzolanas, and that of stones of large 

 dimensions, lavishly used in modern buildings, in s'lite of all the examples 

 to the contrary atlbrded by the Romans and Goths." " We may predict, 

 adds the sagacious In^pector-General, " that some years hence, no other 

 mortar will be allowed in public buildings. When M. ^ icat made Known 

 the first part of his statistical labours on the hydraulic limes ol trance, 

 the Academy decreed to him one of the medals founded by Montyon. 



Let us take the opinion of M. Berthier, the most competent judge of 

 the labours of M. Vicat who could be found in the wliole world. Ihe 

 researches of W. Vicat on limes and mortars ought lo be placed in the rank 

 of the best works due to members of the cor;,.s of bridges and highways. 

 His discovery relative to the manufacture of artificial hydraulic limes is 



of the highest importance In making it public M % icat has- 



acted the more nublv, because he might have made a considerable fortune 

 either by selling the lime or by securing a patent of his invention. 



M. Dumas, (we will quote only those of the greatest celebrity in science) 

 declares in his Ckimk Appluiuf'c uux Arts, that the solution «f "'« '''°S 

 debated question of hydraulic limes is due entirel,, to the labours 

 of M. Vicat. In speaking of artificial pozzolanas the illustrious 

 chemist observes, " It is, however, from labours in '>>« 'f "''^ "^.^ ''^'^.^J: 

 Vicat has been led to the important discovery with which he has enriched 

 the arts. The state in which he found the question renders the discovery 

 the more remarkable." ^ ,,-■.. a 



We could borrow proofs equally flattering from a host of writers, and 

 especiallv from two excellent articles by M. Chevreuil, inserted in the 

 ZLl L Sarants. These opinions, notwithstanding the high authorities 

 ?,om whom the, emanate, ought not, doubtless, to prevent ''je commiss ma 

 from making the minute enquiry of wh.ch the Chamber has beaidthe 

 results, but your commission, since they have by their own researches b en 

 led to the opiuions professed by the Academy of Sciences, and the judg- 

 ments of Gay-LusL, of Beiiier, of Chevreuil, of Dumas of Bruyere 

 desire to avail themselves of a circumstance which proves they have not 



erred. 



Conclusion. 



M.'vrcat' was the first to demonstrate that the properties of natural 

 hydraulic limes depend on clay distributed throughout 'l^^'r substance ha^ 

 is, on a particular action which silex united with alumina exeicises on 

 lime when these substances are brought by heat to a proper state. 



M. Vicat has been the first to make hydraulic lime of all ' '^^ , "o only 

 in small quantities in the laboratory, but in large q"^'" 'f, ^^^'''= ^^ '^f^ 

 tions of his bridge of Souillac. The piers of this ""^le budge rest on a 

 foundation of concrete formed with artificial hydraulic lime Since he 

 labours of M. Vicat, means have been found of procuring, whenever it is 

 necessary, lime, which readily sets lu water. i, u certain 



M. Vicat has liberally given his discovery to he P"bl'<=. I^ ^ "^ hv° 

 that if he had secured by a patent the privilege of making the ai ncial by 

 draulic lime, this engineer would have acquired an •■"»;° \f"'^"."^; . 

 The first discovery of M. Vicat has faded, if the "P'*^^.^/;" "^l "" PfJ, 

 netted, beside the important results deduced from it. \«. ''^^: ^J!^;" "'^ 

 Uidefatigable enginee. traversing France step by ^'^P, seek ng beds olcal 

 careous^narl, clay formations in which were united nat.u> ally in proper 



proportions, the constitutive elements of liyd'-f 1"= l'""^^ '-nme fo siccessfal 

 him during twelve years in this search winch has '^^'^,7f/°^7<^'=j;"i' 

 that there are now known on French ground by the ol'; 1^^""= "Jj^; 

 Vicat 900 quarries capable of furnishing hydraulic limes, while belore 

 U ere were 'reckoned o^ly eight or ten. M Vicat has - "f J^P-^^^' f 

 the houour of having discovered and placed in the '^'^"''^^."/j^^' ""';;'.' 

 such wealth hidden in the bowels of the earth, or been ^^J^f ^ at lU, sur 

 face, that in order to complete this work he has ^«7™^"'^f'li''^,^f;j'"^'„d 

 ment to which his standing and merit give him claims uncontested and 



'" Xwo'ikfof M Vicat on po-.:ola„as have been equally decisive. They 

 ha^ prov d thit the pj:-ent c'lays aflord a'tificial pozzolanas superior, o. 

 at least equal to the Italian; and as nature has ^-stribu ed chiy «ith a 

 kind of profusion on the surface of the globe, °»'f '"^ Pre;;-^^; "^ j^' 

 present day from easily obtaining excellent pozzolana in every regain 

 ^ France, which before the time of W. Vicat, was tr.buaiyto^Lngland 

 for Roman cement, could now supply the wants of ''>« v^l'o'e », ^urop^ 

 The general system of foundations, by means of concrete, dates Irom tne 



* M. Vlca.. appointed divisioo.ry '"r'rZT:j:{,X::^':{^<^^'^^^^^^^^ 

 pritL his rank of eneineer iu duel tu contiuue the investieatiou wiutu 



, commenced. 



