1842.] 



THE CIVIL ENGINEER AND ARCHITECTS JOURNAL. 



169 



preferable to brick shafts, which frequently bang up, and in that case give 

 much trouble, whereas if the iron cylinders do not descend freely, they will 

 bear the application of considerable force to drive tliem down. They are 

 frequently forced tlirough the indurated ferruginous gravel. Light planking 

 is also sometimes used, particularly iu such cases as in the well he is now 

 sinking at Chelsea, which is 20 feet square, lined throughout with 3-inch 

 planking. It has reached the quick sand at a depth of 32 feet, and will be 

 stopped there. 



Mr. Davisou had just completed a well at Messrs. Truman and Hanbury's 

 brewery, with cast iron cylinders, 8 feet diameter, and 193 feet deep, an 

 account of which be promised to present to the Institution. 



The President was now sinking a set of cast iron cylinders through sand 

 which was liable to be washed away ; they were to be fiUeil with concrete 

 and used as the foundation for a lighthouse at tlie Point of .Vir. An account 

 of the construction was, he believed, preparing for the Institution. 



" All Hislorical Account of Capper Sheathing for Vessels." By J. J. 

 AVilkinson. 



The two former papers by the same author,* treated of Wood and Lead 

 Sheathing for Ships : the present communication gives in the introduction a 

 general account of Copper as a metal ; the localities supplying it ; the uses 

 to which it has been applied, from the earliest period to the present time; 

 and the relative estimation in which copper of various countries is held on 

 account of its degree of purity, its ductility, or its better preparation, in 

 ■which latter particular British copper is stated to be pre-eminent. — An 

 epitome is then given of a return to the House of Commons ; whence it 

 appears that in 1832, into Swansea alone, there was imported 4350 cwts. of 

 unwrought metal, and 410,604 cwts. of ore, and that there was exported 

 during the same year, of British metal, 153,742 cwts., and foreign metal 

 112,830 cwts. Copper from Sweden is considered more malleable than that 

 from Hungarj' ; but the former is not so good as British metal, as it contains 

 a portion of iron. 



Copious extracts are made from " Knowles's Naval Architecture," whence 

 is quoted the first recorded use of copper sheathing upon the " Alarm" 

 frigate, in 1761; at that period it was believed that sea water had little 

 action upon pure copper, and the rapid decav of the partial sheathing of cer- 

 tain ships was attributed to the impurity of the metal. Experience showed, 

 however, that pure copper, like that employed on the " Tartar," could be 

 destroyed in the short space of four years, while the sheathing of the " Bata- 

 via," an old Dutch man-of-war, and of the " Plymouth" yaclit, was perfect 

 after 24 and 27 years' service; in both tlie latter there was an alloy of 

 ji^th part of zinc. 



Much information is given on the rolling of copper sheets ; the dimensions ; 

 the weight per square foot of different gauges, and the uses to which the 

 various kinds are applied : as also on the quantities of metal used for sheath- 

 ing. The " Xeptune," of 120 guns, was cased with 4738 sheets, weighing 

 altogether 17 tons 19 cwts. 



The use of copper sheathing is to protect the wood from destruction by 

 the worm, and to prevent the adhesion of weeds, barnacles, &c. which 

 impede the sailing of the vessel. On the first introduction of copper, it was 

 used in conjunction with iron bolts and other fastenings ; these soon oxidated, 

 and serious accidents occurred. It was advised in consequence that all the 

 bolts should be of copper or mixed metal. The attention of the Government 

 was directed to the subject, and Sir Humphrey Davy was appointed to ex- 

 periment upon specimens of metal of different qualities. He soon discovered 

 that when two dissimilar metals are in contact and immersed in sea-water, a 

 voltaic effect is produced which occasions a rapid corrosion of the more oxi- 

 dable metal, while the other remains uninjured. In 1S24 Sir Humphrey Davy 

 communicated to the Government that he had discovered a means of pre- 

 venting the corrosion of the copper by rendering it electro-negative. This 

 he proposed to effect by protectors of zinc, iron, or any other easdy oxidable 

 metal : after a variety of experiments he determined that the protectors 

 should consist of six bars of cast iron, whose united surface should be Tji^rth 

 part of the area of the copper exposed to the action of the sea water : two 

 of them were placed midsliips on the keel of the ship, two on the bows, and 

 two on the stern about three feet under water. As far as the philosophical 

 fact was concerned, the result was conclusive, as the copper suffered no waste. 

 Inconveniences, however, arose which had not been foreseen : as tlie copper 

 did not oxidate, its whole surface was speedily covered with barnacles and 

 sea weeds, which collected in such quantities as to impede the sailing of the 

 vessels, and adhered so fast that in removing them the copper was frequently 

 torn away : the protectors were therefore abandoned, in 1826, for all vessels 

 on service, but were still used for the ships lying up in harbour ; the bottoms 

 of these became, however, so foul, that in 1828 the system was entirely 

 abandoned. After the protectors had been for some months on the ships' 

 bottoms, it was found that on the outer surface a red oxide was formed, and 

 beneath it, for some depth, a sul)stance resembling plumbago ; this substance, 

 having sulphate of iron for one of its constituents, when laid upon any 

 inflammable body, caused spontaneous combustion : a similar result was 

 obtained by Mr. F. Daniel in 1817, while experimenting upon cast iron, by 

 solution in dilute muriatic acid. Protectors of various kinds have been tried 

 in the French navy, and in the United States ; but generally with doubtful 

 success. 



* Minutes of Proceedings, vol. 4, for 1841, pp. 318 and 35 



A list of all the patents for copper and other sheathing, as well as means 

 of preventing corrosion, &c., is then given at great length : the gradual 

 progress of the application of copper sheathing, first to ships of the Royal 

 Navy, then to Indiaracn, to Transports, and finally to Merchant Ships, is then 

 traced. It appears that of the vessels which enter the Thames, one-fifth are 

 sheathed with copper aud its alloys ; of vessels at Liverpool, eight-tenths are 

 coppered. The precautions for preserving uncoppered vessels from the 

 " Teredo navalis" are then described : and coal-tar pitch is mentioned as the 

 most effective substitute for sheathing. 



Copper sheathing appears to be entirely neglected for vessels in the coal 

 trade, although it is singular tliat the " Teredo" is found in every port to 

 which coals are carried, south of the Tees ; in the Thames, as high up as 

 Gravesend, and northward as far as Whitby ; traces of the ravages of the 

 " Teredo navalis," and of the " Limnoria terebrans," have at various periods 

 been found, from the north of Scotland and Ireland, on almost every coast 

 to the Cape of Good Hope and Van Diemen's Land, in the Eastern hemis- 

 phere : and in the Western hemisphere, from the river St. Lawrence to Staten 

 Island near the Terra del Fuego, almost in the Polar Sea ; so that although 

 this maritime scourge is rifest in warm climates, yet cold latitudes are not 

 exempt from it. 



Remarks. — Mr. Lowe was pleased to find th.it the use of coal-tar pitch for 

 shipping was advantageously mentioned : he was convinced tliat it would be 

 found very superior to vegetable pitch : he had seen comparative experiments 

 tried on board an India ship, and the result was, that the timber which had 

 becu coated with the former was preserved both from the worm and from 

 decay, while that which was covered with the latter had sufi'ered from both. 

 He attributed the preservative quality of the coal-tar pitch to the quantity of 

 sulpho-cyanic, or sulpho-prussic acid, which it contained. 



Mr. Home had used coal-tar extensively on wood, but found that it pro- 

 duced decay, which he attributed to the ammonia contained iu it. 



Lieutenant Oldfield alluded to Renwick's patent, for saturating timber with 

 coal-oil : he had seen specimens of piles at New York, which, when prepared 

 by Renwick's process, perfectly resisted the attacks of the '■ Teredo navalis," 

 in the same situations where " kyanized piles" had been entirely destroyed. 



Mr. Bethell confirmed Lieutenant Oldfield's statement. Coal-oil was a 

 powerful preservative when properly prepared and applied : he objected to 

 the use of ammonia in any shape, as it rotted timber very fast. In experi- 

 ments he had made, previously to taking out his patent for preparing timber 

 with coal-oil, he observed that wood coated with common coal-tar soon 

 turned brown, and decay ensued : ammonia produced the same appearance 

 and effect. If any vegetable fibrous substance, such as peat, was sprinkled 

 with ammonia, it speedily rotted, and became a rich black earth. In the 

 Jlediterranean, the native ship owners used nothing hut coal-tar pitch for 

 their vessels ; they were cleaned and well tarred twice a year, and the worm 

 seldom made any ravages, although unprepared timber in those latitudes was 

 destroyed in a very short time. The refined coal-tar, as manufactured in 

 London, is purified from ammonia by distillation, and found an excellent 

 coating for wood. The oil of tar, used in Mr. Bethell's process, is likewise 

 purified from ammonia. 



Mr. Parkes conceived that diluted ammonia must be meant as recommended 

 for agricultural purposes, and not the ammouiacal liquor as it came from the 

 gas-works ; the former, when used with discretion, properly diluted, and to 

 certain soils, was an active stimulant in cultivation, but the latter contained 

 matter which was very prejudicial. 



.Mr. Bethell observed that ammoniacal liquor, when diluted with three 

 parts of water, had been found to succeed perfectly with peaty soils. Nearly 

 all the sal ammoniac of commerce is now made from the ammoniacal liquor 

 from gas-works. 



Mr. Hawkins remarked, that it could he readily understood that the pro- 

 portion of ammonia used would regulate the effect to be produced ; as in the 

 case of gypsum, of which two bushels per acre was a good manure; but in 

 some places fifteen or twenty bushels per acre had been tried, and of course 

 a complete failure had ensued. 



Mr. Parkes replied, tliat gypsum was commonly used in Yorkshire, and 

 habit had dictated the proportions so well that it seemed to be the best 

 manure the farmers possessed there. 



-Mr. Taylor recalled the conversation to the subject of the Paper on Copper 

 Sheathing ; from which many curious facts might be drawn. The ancient 

 specimens of copper sheets had endured longer than the modern : the former 

 contained an alloy of irio*'' P^'''' °^ ''""^' The " Muntz" metal, which is 

 now being extensively used, contains alloy of the same material, but in a 

 larger proportion. The inequality of manufactured copper ha<l perplexed the 

 chemist and the manufacturer for full forty years ; aud after all their re- 

 searches and experiments, it would appear that the chemistry of the manu- 

 facture of copper and of iron was not understood. Mr. Taylor had been 

 consulted by Sir John llenslowe on tlie subject, and he had recommended 

 assaying the sheets instead of receiving them by the appearance of their 

 surfaces, as was the usual mode. Dr. Faraday and Mr. Ricliard Phillips had 

 made an extensive series of experiments for Mr. Vivian, aud Mr. Farquharhad 

 carefully analysed various specimens; but all these eminent men faileil in dis- 

 covering any chemical difierence between the copper which had endured well 

 aud that which had been rapidly destroyed. Sheets of copper rolled the same 

 day, under apparently similar circumstances, differed materially iu quaUty. In 

 the process of " polling," which is carried on by stirring about the copper 

 while in a fluid state with poles of green wood, producing ebullition, whetUer 



2 B 



