1843.] 



THE CIVIL ENGINEER AND ARCHITECT'S JOURNAL. 



229 



perfected throughout ? — must there almost always be something to 

 operate as a drawback on our satisfaction, and to mar our enjoying 

 what we might else admire ? To mention economy in such cases by 

 way of excuse, is no apology at all; — it is like buying a costly pic- 

 ture-frame and hanging it up empty, because you cannot afford or 

 else begrudge the money to purchase a painting to put into it; and 

 though it is done every day, it is a very strange kind of economy 

 that induces people to spend their money merely, it would seem, to 

 convince the world that they lack either the means or spirit to do 

 handsomely what else there is no occasion to do at all. 



Possibly, however — and we are willing to hope that such will be 

 the case, it may still be intended to complete what is here begun, 

 and that as a screen has been added to the house, a house will in 

 due time be added to the screen — that is, a facade on this side, of 

 corresp onding character. If not, we can account for what has been 

 done, only by supposing that the noble owner has built chiefly for the 

 gratification of his own eyes — not so much with any idea of improv- 

 in g the appearance of his house — which now looks more insignifi- 

 cant than before, as for the purpose of providing a beautiful archi- 

 tectural object to be seen from his own windows, so that in fact he 

 may be said to have followed Lord Chesterfield's advice, and erected 

 a front " over the way " for himself to contemplate. 



That the effect of the screen as beheld from the house must be 

 very striking, and form quite an architectural picture, there can be 

 no doubt, and not least so of all when lighted up by gas at night. 

 But then, besides that such consideration does not reconcile us to so 

 much being left undone, by carrying out the ideas suggested by the 

 screen, the whole space between that and the house might have been 

 ren dered a highly ornamental, though rather small cortile, whereas at 

 present, it has no architectural character, or no more than what 

 amounts to a sort of apology for something of the kind. Indeed, if 

 nothing further is now to be done, it becomes a question whether it 

 would not have been better to make the screen more of a screen than 

 it now is, by filling up the intercolumns, for about half their height, 

 with metal work of the same pattern as the gates. In this there 

 would have been novelty, and certainly no inconsistency. There were, 

 besides, many other ways by which the same purpose could have 

 been accomplished, and as one of them we may mention that of 

 adopting for a design of the kind, an order of square pillars instead 

 of columns, raised not on a stylobate but merely a socle, with inter- 

 columnar screens of masonry between them carried up to the level of 

 the imposts of the archways : in which case the lamps would be 

 placed on those screens, and these last might be embellished with bor- 

 dered sunk panels (in the manner of those now over the two doors 

 at the ends,) with reliefs, not in stone but bronze. 



We have said nothing as to the absurdity imputed to the idea of a 

 row of pillars or columns employed merely as a wall — at least as a wall 

 with openings in it. The objections urged against it as being such, ap- 

 pear to us pedantical and hypercritical. Columns, we grant, were not 

 originally intended for such purpose, but it does not therefore follow 

 that a different application from the one originally contemplated must 

 necessarily be bad in itself. Were such the case, we must abandon 

 much that is now considered perfectly legitimate, and is tolerated, if 

 not always admired. If, too, absurdity there be in using columns that 

 support nothing but their own entablature — which then becomes the 

 top or coping of the perforated wall described by those columns ; — 

 how much more extravagant, and remote from the original purpose of 

 columns must it be to employ them singly: and without their having 

 anything at all to support, except it be a "black image" perched 

 \ipon the top of the capital, yet not looking so much as if it had 

 alighted from heaven, as if it had ascended from the infernal regions. 

 If, therefore, we can endure absurdities of that kind, merely because 

 anti quity has left us some precedent for them— of which, however, 

 our modern copies fall very far short indeed— we may surely recon- 

 cile ourselves to what, while it is a degree or two less absurd and a 

 less preposterous conceit, can hardly fail to produce a strikingly pic- 

 turesque perspective effect, let the design itself, considered apart 

 frofn such effect, be what it may. 



CONSTRUCTION OF A BETON BRIDGE. 



Description of a Bridge of B<ton,' constructed at Grisoles, in the 

 Department of Tarn-el- Garonne, in France. By M. Lebrun, 

 Architect if Montaaban. 



Translated for the Journal of the Franklin Institute, from the " Bulletin de 

 la Soeiete d'Encouragement pour I'lndustrie National," for July, 1842. 

 By Ellwood Morris, Civil Engineer. 



Living in a region where suitable building stone is scarce and ex- 

 pensive, and where brick masonry alone is used, M. Lebrun, guided 

 by the fine works of M. Vicat, on hydraulic limes, conceived the idea 

 of substituting for this masonry the beton, which the Romans used 

 with so much advantage. 



In consequence, he submitted, in 1S39, to the Minister of Public 

 Works, the project of a bridge entirely of beton, which he offered to 

 construct on the lateral canal of Garonne, to be traversed by many of 

 the royal and departmental routes, this offer having been accepted, 

 under certain conditions, M. Lebrun commenced his work in June, 

 1840. 



The lime was of the hydraulic quality, burnt in perpetual kilns, by- 

 pit coal. The sand was clear of all earthy particles, of fine grain, and 

 pretty uniform. The gra vel slones, of the size of a hen's egg, came 

 from the river Garonne. The lime was slaked alternately in two ba- 

 sins, joined together. For this purpose, we poured at first, in one of 

 the basins, a quantity of water proportioned to that of the lime which 

 we wished to slake ; we then put in sufficient quicklime for the water 

 to cover it ; then we left the lime to slake freely without disturbance, 

 except by taking care to prick it, from time to time, with a stick, to 

 introduce the water into those parts of the basin where the dissolved 

 lime was dry. When the fermentation had ceased, we stirred up the 

 lime in every direction with an iron hoe, in order to mix the paste, 

 and render it homogeneous ; we left it then in this state, not to be 

 used for twelve hours after slaking. 



The proportions observed by M. Lebrun for beton destined for the 

 construction either of walls or arches, were, in every ten parts, com- 

 posed of two parts of lime in paste, three parts of sand, and five 

 parts of gravel stones, or pebbles. 



For making the mortars, we placed, on a paved surface, two mea- 

 sures of the slaked lime, which, after having been well beaten with 

 pestles of cast iron, softened again by yielding up a part of the water 

 with which it was charged ; then we placed beside it three measures 

 of sand, which we mixed, little by little, with the lime, always having 

 the aid of the pestles, and stirring the whole with the shovel and hoe, 

 in order that all the parts of the sand should be well incorporated, 

 observing not to put any water into the mortars, but, if the sand was 

 too dry, we moistened it, a few moments before mixing. As soon as 

 the mortars were sufficiently manipulated, we added five measures of 

 grave! stones ; the whole was then long and forcibly mixed and 

 pounded, until each part of the gravel was sufficiently enveloped by- 

 mortar ; then the bHons were taken in quantity, to wait for the mo- 

 ment of being used. We took care to make only what we could em- 

 ploy in a day's work, without which precaution it would have lost its 

 cohesion. 



The 15th of June, 1840, the excavation of the foundations of the 

 two abutments being done, we commenced laying the beton, taking 

 care, each time that a layer, or course, was finished, to cover it up 

 immediately with wet mats of straw, to prevent a too rapid drying 

 by the heat of the sun. By means of this precaution, the new course 

 connected itself more intimately with the one below. We continued 



1 The French beton is nearly identical with the English concrete, the 

 main difference being in the manipulation ; thus beton is composed of lime, 

 sand, and small pebbles, or broken stone, taken separately, and successively 

 mixed together, the pebbles being added last ; while concrete is usually- 

 formed of lime, mixed directly with gravel, containing naturally about the 

 due proportion of pebbles and sand ; proper quantities of water being used, 

 and the factitious stone resulting, in both cases, being in effect the same. 



Beton, or concrete, has before been used in retaining walls and other con- 

 structions, and, as is stated by General Pasley, of 11. E. JJ. corps of En- 

 gineers, (in his admirable Treatise on Calcareous Cements,) it was also ap- 

 plied experimentally to build a military casement near Woolwich, of which 

 the arch had 18 feet span, 5 feet rise, and 6 feet depth at the crown, and 

 which, when subjected to the direct fire of 21 pounder (;uns, as well as the 

 vertical plunge of 13 inch shells, loaded to weigh 2001b. each, resisted both 

 with success, and, contrary to expectation, was less injured by the latter, 

 than by the former. 



We must, however, here observe, that the failure of the «oncrete wharf 

 walls, at Woolwich and Chatham, in consequence of tidal exposure, and the 

 necessary protection of the concrete sea wall at Brighton, with woodwork, 

 to shield it from the action of water in mass, (as mentioned by General 

 Pasley,) points out the necessity of confining the application ol concrete to 

 constructions within reasonable and proper limits. 



31* 



