380 



THE CIVIL ENGINEER AND ARCHITECT'S JOURNAL. 



[November, 



no visible amount of abrasion, and Captain Ilandcock contended that the 

 practice confirmed his previous ideas. 



Mr. Field thought the form of the axles a decided improvement. They 

 were somewhat on the principal of those which had succeeded so well for 

 common roads, and he believed that they must prove of considerable advan- 

 tage for railways. 



Mr. Fairbairn approved of the construction of the journals, and had no 

 doubt of their practical efficiency; he particularly liked the cones, as in ad- 

 dition to their affording the means of preventing lateral motion and dimi- 

 nishing the friction, their form added strength to that point near the shoulder 

 where it was most wanted. 



Captain Handcock stated that the average consumption of oil on railways, 

 was for an engine and tender with common axles and brasses, about 6 lb. for 

 110 miles ; of this quantity, 2 lb. were used for lubricating the axles. 



General Pasley observed that bis attention had been drawn to these axles, 

 and although on account of his official position, he scrupulously avoided 

 giving any opinion on the merits or dements of an invention, yet he might 

 say that if he was a proprietor of a railway, such was his opinion of Captain 

 Haudcock's axles, that he certainly would give them a trial. 



" On the application of Zinc by the process of Electro-deposition, for the 

 preservation of Iron, as applied to Engineering and other purposes." By 

 Frederick Pellatt. 



The object of the paper is to direct attention to the properties of zinc as 

 a protecting coating for iron ; to describe the processes already employed for 

 that purpose ; the reasons of their failure, and the peculiar fitness of the 

 process of electro-deposition of metal for the purpose. Iron is, it is stated, 

 from its superior affinity for oxygen, liable to rapid decomposition, and it 

 has ever been a desideratum to discover some cheap mode of protecting it ; 

 the ordinary methods of painting aud tinning uot being sufficiently lasting. 

 By the laws of electricity, when metals are in contact, the negative metal is 

 protected at the expense of the positive : and under all ordinary circum- 

 stances zinc being the positive metal, it becomes a protector to the negative 

 metal — iron. Zinc, like most metals in commerce, is not to be met with 

 pure ; in the other metals, however, the impurities do not generally tend to 

 the injury of the metals with which they arc combined ; such, however, is 

 not the case with zinc and its impurities, as when in contact with moisture, 

 they generate a galvanic action by which the zinc is rapidly destroyed. Those 

 who have made use of zinc, especially where it has been exposed to exciting 

 fluids, such as milk, or any other fluid easily converted into acid, are well 

 aware of the rapidity of its destruction. The impurities existing in ordinary 

 zinc are then noticed, as well as the difficulty and costliness of the process 

 uf sublimation, in order to refine it. It is also contended that impure zinc 

 being in itself so easily destructible, is of little value, as it cannot afford 

 protection to any other metal which may be coated with it : and therefore 

 the mode of plating iron with melted zinc (of commerce!, must be objec- 

 tionable. 



The Report made to the French Academy by Monsieur Dumas, is quoted, 

 in which he says : " the zincing of iron by steeping it in a bath of melted 

 zinc, has many inconveniences : besides, the iron combining with the zinc, 

 constitutes a very brittle superficial alloy, the iron losing its tenacity. The 

 presence of foreign matters used in the process, in order to keep the zinc in 

 fusion, increases the amount of impurity, and being less fusible than the 

 zinc, a great loss is created in consequence of the zinc volatilizing at a high 

 temperature. It is well known that in the dtposition of metals from me- 

 tallic salts by the electro-process, the pure metal only is deposited, so that 

 the process described in the paper, is not open to the objections against 

 ordinary metallic coatings. The iron also being coated with zinc in a cold 

 solution, its state is in no way changed. The expense of the process is stated 

 net to exceed that of four coats of oil paint. 



Though to men of science the properties of zinc in connexion with other 

 metals have been well known, (and the opinion of Drs. Graham, Kane, 

 Daniel, and Monsieur Dumas, are quoted on the subject,) yet practically this 

 knowledge has not been much applied, chiefly from the difficulty of obtaining 

 pure zinc. The electro process, it is stated, entirely overcomes the diffi- 

 culty; at the same time it affords facilities for covering iron-work of any 

 form or size, and as it requires no great outlay, the process may be carried 

 on in any locality. Zinc has another great advantage : although it is easily 

 oxydized, the oxyde in ordinary circumstances is insoluble, and affords a 

 protection to the metal below. For roofing and many other purposes, of 

 which a long list is given, it is suggested that zinced iron would be found 

 very useful. 



Remarks. — Mr. F. Pellatt exhibited a number of specimens of iron covered 

 with zinc and copper by the process of electro-deposition, which he de- 

 scribed. The pieces of iron were first rendered perfectly clean and free from 

 oxyde by plunging them into a bath of heated sulphuric acid and water : they 

 were then placed in a cold solution of sulphate of zinc. The positive pole 

 of a galvanic battery being attached to a zinc plate, and the negative pole to 

 the piece intended to be covered with metal, the deposition commenced 

 equally all over it, and was continued as long as was considered necessary. 

 By this process the pure metal alone could be deposited, and the amalgama- 

 tion of the zinc and iron, which occurred when the iron plates were dipped 



into melted metal, was avoided. For zincing, he preferred an acid to an 

 alkaline solution of the metallic salts. Some thin plates, which had been ex- 

 posed for eight months, on roofs iu London, did not exhibit any appearance 

 of rust. The process could be applied on any scale, as all the apparatus that 

 was necessary was some wooden troughs to contain the solution and the 

 pieces of metal to be covered. He had not made accurate experiments as 

 to the efficacy of the process, when applied to iron exposed to the action of 

 sea- water, but he feared the result, on account of the formation of muriate 

 of zinc. 



The President said the subject was one of great importance to engineers, 

 as if the deposited coating was found to stand the test of time, it would 

 enable the use of iron to be extended ; but the main point to which he 

 would direct Mr. Pellatt's attention was the defence of cast-iron from the 

 destructive action of sea water. 



May 28. — The President in the Chair. 



" Account of some Egyptian Bricks from the Pyramids of Dashoor" 

 By J. 1'erring. Communicated by William Newton, Assoc. Inst. C. E. 



The author states that the ancient Egyptians used bricks for every'purpose, 

 except for the erection of temples and tombs ; that they were generally 

 crude bricks dried in the sun, and in the dry climate of Egypt they sufficed 

 for all ordinary purposes. The only instances in which he found they had 

 been subjected to the action of fire, were for a quay-wall, aud for the found- 

 ations of a town near the Nile in a damp situation. From the drawings in 

 the tombs, and the narrative of Holy Writ, it would appear that the captives 

 were generally employed in manufacturing bricks, and as many are found 

 with the name of the reigning monarch stamped upon them, it is not im- 

 probable that they constituted a government monopoly. It is a curious fact 

 in connexion with the Biblical account of the labours of the Jews, that more 

 bricks bear the stamp of Thothmes III. than of any other monarch; and 

 according to Wilkinson and other learned authors, it was during bis reign 

 that the exode of the Israelites took place. 



The bricks, which are 16 in. long, 8 in. wide, and about 5 in. thick, are 

 made of the alluvial soil of the valley of the Nile, mixed up with chopped 

 straw to bind the whole together. They were formed in wooden moulds, 

 and dried in the sun. It would appear from drawings, that the earth was 

 tempered and the straw was mixed in, by men treading the mass with their 

 feet. With such bricks as these the Egyptians formed the walls of their 

 towns, using the alluvial earth also as mortar. The author states that he 

 found some remarkably well. formed arches, of 12 ft. to 1-1 ft. span, built in 

 concentric half-brick rings, at Thebes, the bricks of which were marked with 

 the name of Scsostris ; consequently they must have remained uninjured by 

 time upwards of 3,180 years. They all have a cavity in the sides to retain 

 the mortar, similar to what is practised in modern bricks. 



The pyramid from whence these bucks were taken, was built, according 

 to Herodotus, by a king named Asychis, who lived about 2000 years before 

 the Christian era. The body of the pyramid is composed entirely of crude 

 brick, but it bad an external casing of limestone as a protection from the 

 action of the weather. The author says that not a single brick appears to 

 have settled from its place, aud that it is difficult to imagine a mass more 

 solid and compact, iu spile of the great pressure the bricks had to support 

 in a pyramid of 215 feet high. 



Deposit in Pipes from a Brewery. 



Mr. Davison presented a piece of copper pipe, in. diameter, through 

 which the wort bad been forced during a considerable period, at Messrs. 

 Truman, llanbury, and Co.'s brewery. It was nearly stopped up by a de- 

 posit of a black substance, which opposed such resistance to the passage of 

 the fluid as to induce an examination of the pipes, and the discovery of their 

 state. 



Dr. Ure said that the deposit was a good example of what Lcihig called 

 " Ereniacausis " — product of slow combustion. The substance was a carbo- 

 naceous matter, resulting from the slow combustion of the gluten and starch 

 contained in the brewers' worts. 



May 30. — The President iu the Chair. 



Corrosion of Iron and Steel. 



" On the action of Air and Water, whether fresh or sail, clear or foul, 

 and at various temperatures, upon Cist and Wrought iron, and Steel." By 

 Robert Mallett, M. Inst. C. E.' 



The author iu this paper gives the completion of his researches upon this 

 subject, on which he has been engaged for nearly five years, during the in- 



1 This paper, which forma the continuation of the ctmmunication which 

 nas read I elorr tin- Institution, May 26, 1840, (Minutes of Proceedings, 

 Journal, Vol. ill., p.i'li,) occupied the attention of the meetings on t»o 

 eve ings. 



