2G0 



THE CIVIL ENGINEER AND ARCHITECT'S JOURNAL. 



[August, 



Wlien the Column in the Place Vcndnme was erected, the same 

 faults were repeated ; a bargain was made with an ironfounder, who 

 had never been engnged in bronze work, he however had the temerity 

 to undertake the moulding and finishing at one franc per kilo. C^(l. per 

 2 Ih.) The government on the other side undertook to deliver to him 

 in guns, taken from the Russians and Austrians during the cani))aign 

 of 1805, the quantity of bronze necessary for the completion of this 

 enormous monument. The founder used a furnace he had for casting 

 iron, but not being aware of the phenomena of bronze casting, and 

 urged by his vanity to attempt in the first instance the casting of 

 several uf the great pieces of the base of the coKunn, he encountered 

 several defeats. Each time he necessarily altered the alloy by oxidiz- 

 ing the tin, lead and zinc, which metals so oxidized passed into the 

 scoriae or were carried off by the current of warm air. He did not 

 perceive this cause of continual loss, and continued to produce the bas 

 reliefs; but it may be readily conceived that they contained more 

 copper than the bronze of the'guns. When the founder had got two 

 thirds through the column, lie found out that he had got uo more metal, 

 ■and being, according to contract, responsible for the metal delivered 

 to him, he was at once ruined. In this lamentable situation he tried 

 to melt up the white metal obtained from the reduction of the scoriae, 

 and a large quantity of refuse metal which he had bought up at a low 

 price. The bas reliefs which he obtained from the mixture of all 

 these materials were marked with blotches and lead spots, their colour 

 from a dirty grey became quite black ; the authorities refused to re- 

 ceive work so defective, and put his foundiy under sequestration. 

 He succeeded, after much petitioning, in obtaining a committee to 

 examine his accounts, which was composed of two chemists, two 

 architects, two mechanical engineers, and two founders, with an auditor 

 of the Council of Slate for the chairman. The weight of each piece 

 delivered by the founder was known; specimens were taken from 

 them, and the proportional parts weighed, from which was made an 

 ingot representing the mean composition of the whole column. It was 

 then found by analysis that it contained : 



Copper - - - 89-140 



Tin .... 7.200 



Lead - - - - 3-313 



Silver, zinc, iron - - 0-047 



100 

 The committee then took specimens of bronze from the guns re- 

 maining in the government stores, and an ingot was formed to repre- 

 sent as nearly as possible the mean composition. The analysis of this 

 ingot gave the following proportions: 



Copper - - - 89-3iiO 



Tin .... iu-0-10 



Lead .... 0-10-2 



Silver, zinc, iron, loss - 0-40S 



100 



It was further known, that the law in France had fixed the composi- 

 tion of gun metal at 90 parts of copper and 10 of fin per cwt., but that 

 this law was never well executed, and during the revolution scarcely 

 attended to at all ; it was also known that these foreign guns were of 

 a more complicated and baser alloy than the Frent-li. Taking all 

 these circumstances into consideration the committee were of opinion 

 that the founder had produced an alloy, if not superior, at least equal, 

 to that which had been given to him; and that they considered that 

 he could not be charged with fraud in his contract. The chemical 

 operations fuither explained the whole proceeding; by making separate 

 analyses of the specimens of the great bas reliefs, the shaft, and the 

 capital, it was found that the first had only 0-OG alloy per quintal ; the 

 second, particularly towards the upper part, and the third contained 

 as much as 0-21. It was therefore evident that the founder not know- 

 ing how to manage bronze, had refined his alloy by several times re- 

 melting, and consequently diminished the total weight, and that to 

 make up for this loss, he was obliged to put into the last castings the 

 white metal extracted from tlie scoria. Thus he had given bronze of 

 too good alloy in the beginning, which had obliged him at last to make 

 the alloy too low. The moulding of the several bas reliefs was so 

 badly executed, that the chaser employed to go over them, removed 

 by chiseling or filing, a weight of bronze equal to 70,000 kils. (7 tons), 

 ■which were given to him, besides a sum of 300,000f. (£12,000) paid 

 down. 



It was certainly hard to pay so dearly for experience, but fortunately 

 it was profitable ; not however that all the subsequent bronze works in 

 France have been more successful, for the founders liad to submit to 

 several severe checks, and were obliged to study the processes, and 

 proportions necessary to form a good alloy. Thus when in 1817 Lemot 



was employed to cast the equestrian statue of Henry 4th, now on the 

 Pont Xeuf, he at least took the precaution to take specimens from three 

 bronze statues of Keller at Versailles, which were the best, with re« 

 gard to casting, green colour, and the grain. The following is the 

 result of his analvsis. 



100- 



100- 



100- 



100- 



Lemot thought that he had gained experience enough from these 

 analyses, but he did not escape from serious difficulties during the 

 casting. Wishing to make use of the furnace, which had been built 

 for casting the equestrian statue of Louis loth, formerly in the Place 

 de la Concorde, but the furnace not having sufficient draught for the 

 fusion of Keller's alloy, in which there was more copper than in that 

 of the statue of Louis 15th, he was obliged after several trials to make 

 great changes, and still the casting did not perfectly succeed. The 

 body of the king had several hollows in it, and the belly of the horse 

 failed, a hole so large having been formed that it was obliged to be 

 filled up; further 14,000 kilo. (14 tons) of oxidized rubbish was sold 



off- 

 Casting in bronze, although presenting only slight difficulties in the 



manufacture of objects of small dimensions, has always required greater 

 responsibility when it is required to form considerable masses, per- 

 fectly homogeneous. The component metals are deficient in energetic 

 affinity for each other, when in fusion tend to separate in the order 

 of their densities, and, when the less fusible begin to solidify, the 

 others in a liquid state, rise up towards the top, where the easy 

 oxidation of a component part of the alloy always causes the risk of 

 refining the metal. Besides these great obstacles, others are encoun- 

 tered in calculating the several component parts of the bronze, where 

 it is wished to obtain precisely the required quantity of metal for the 

 object to be cast, also in the preparation of the model, the construction 

 of the furnace, and the disposition of the moulds. These and other 

 difficulties explain bow many abortive attempts sometimes preceded 

 in former days the casting of a large work in bronze. They point out 

 why Falconnet was 15 years casting the equestrian statue of Peter the 

 Great, which figures on an immense monolithic pedestal at St. Peters- 

 burg; why the Kellers were 9 years casting the statue of Louis 14th; 

 why Bouchardon and his successor Pigalle took 8 years for that of 

 Louis 15th, on the Place de la Concorde ; why the statue of Desaixi 

 and we may almost say the Column of the Place Vendome, failed, and 

 why the great equestrian statues we have mentioned did not come 

 perfect out of their moulds. The statue of Peter the Great was ob- 

 liged to be begun again from the knees of the Czar and the breast of 

 the horse, to the top of the statue. Bouchardon had much trouble in 

 restoring the delicate forms of the horse in his beautiful equestrian 

 statue of Louis 15th, which were badly produced in the lower part, 

 and we have related the difficulties encountered by Lemot and Piggiani 

 in casting the statue of Henry the 4th, difficulties which lasted four 

 years. We cannot better finish this essay than by mentioning those 

 which have just been surmounted in casting the various parts of the 

 July Column, and for the better effecting this we shall compare it with 

 the Column of the Place Vendome, which is the only one having any 

 analogy to it. The Vendome Column is only coated with bronze, and 

 the largest pieces are only five yards in extent, while each of its tam- 

 bours is composed of six pieces, and the whole cost of the column in 

 specie and metal provided by the state was 2 millions (£80,000). 

 The July column on the other hand is entirely of bronze, and each 

 tambour is in one piece, the base of the column extends about 16 yards, 

 and the capital at the most extended place has the enormous dimen- 

 sion of 26 metres, 85 feet. This column however only cost 1,17-2,000 

 francs (£46,880). 



Inequalities in the thickness of the parts constitute one of the great 

 difficulties of casting, because the thin parts cooling rapidly, and the 

 thick parts slowly, the shrinking of the former taking place sooner 

 than that of the "latter is apt to split the metal. It may be also con- 

 ceived that the shrinking of a large object is so much more than that 

 of a small one, as its dimensions are greater, and the necessity for 

 taking this into consideration causes a fresh difficulty in the construc- 

 tion of the mould, which must be calculated so as to provide for the 

 contingency. It is easy in the same way to conceive that the least 

 motion of the mould, during the operation, will cause the required 

 thickness to be exceeded. These considerations will explain the 

 difficulties which had to be surmounted in casting the several parts of 

 the Column of July, and as to th^ statue we cannot do better than re- 



