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INSTITUTION OF CIVIL ENGINEERS.-MINUTES OF PROCEEDINGS OF SESSION, 1842.

February 15.

“An Historical Account of Copper Sheathing for Vessels." By J. J. Wilkinson.

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 1839, into Swansea alone, there was imported 4350 cwts. of unwrought metal, and 419,604 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 Hungary; 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 decay of the partial sheathing of certain 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 Batavia, an old Dutch man-of-war, and of the Plymouth yacht, was perfect after 24 and 27 years' service; in both the latter there was an alloy of part of zinc.

Much information was 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 sheathing. The Neptune, of 120 guns, was cased with 4738 sheets, weighing altogether 17 tons 19 cwt.

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 oxydated, and serious accidents occurred. It was advised in consequence that all the bolts should be of copper or mixed metal. The attention of Government was directed to this subject,

and Sir Humphrey Davy was appointed to experiment 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 oxydable metal, while the other remains uninjured. In 1824 Sir Humphrey Davy communicated to the Government that he had discovered a means of preventing the corrosion of the copper by rendering it electro-negative. This he proposed to effect by protectors of zinc, iron, or any other easily oxydable metal; after a variety of experiments he determined that the protectors should consist of six bars of cast-iron, whose united surface should be th part of the area of the copper exposed to the action of the sea-water: two of them were placed midships 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 the copper did not oxydate, 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 oxyde was formed, and beneath it, for some depth, a substance 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.

A list of all the patents for copper and other sheathing, as well as for 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 Indiamen, 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 and 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 that 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 Hemisphere; 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.

Mr. Lowe was pleased to find that the use of coal-tar pitch for shipping was advantageously mentioned: he was convinced that 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 been coated with the former was preserved both from the worm and from decay, while that which was covered with the latter had suffered 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. Horne had used coal-tar extensively on wood, but found that it produced decay, which he attributed to the ammonia contained in 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 experiments 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 Mediterranean, the native ship-owners used nothing but coal-tar pitch for their vessels: they were cleaned and well tarred twice ayear, 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 ammoniacal 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 be readily understood that the proportion 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, that 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 th part of zinc. 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 had perplexed the chemist and the manufacturer for full forty years; and after all their researches and experiments, it would appear that the chemistry of the manufacture of copper and of iron was not understood. Mr. Taylor had been consulted by Sir John Henslowe on the subject, and he had recommended assaying the sheets instead of receiving them by the appearance of their surfaces as was the usual mode. Dr. Farady and Mr. Richard Phillips had made an extensive series of experiments for Mr. Vivian, and Mr. Farquhar had carefully analysed

COPPER SHEATHING-PRESERVATION OF TIMBER.

various specimens; but all these eminent men failed in discovering any chemical difference between the copper which had endured well and that which had been rapidly destroyed.

Sheets of copper rolled the same day, under apparently similar circumstances, differed materially in quality. 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, whether the operation is continued too long or too short a time, the metal becomes brittle and the quality cannot be recovered.

Less copper is now exported from Russia because the attention of the miners is directed to the gold mines. Mr. Taylor attributed the superiority of the quality of the foreign copper to the ore being smelted with charcoal; whereas English copper is smelted with bituminous coal, frequently containing sulphur.

March 8, 1842.

"Description of the Tanks for Kyanizing the Timber for the permanent Way of the Hull and Selby Railway." By John Timperley.

Upon the recommendation of Mess. Walker and Burges, the engineers, it was determined that the sleepers of this railway should be kyanized in close vessels, using exhaustion and pressure, instead of in the open tanks usually employed. The present communication, which includes a description of the kyanizing vessels, and an account of the various circumstances connected with the operation, commences by describing the apparatus, as shown by the accompanying drawing, to consist of two tanks, a reservoir, two force pumps, and a double air-pump. The tanks are cylindrical, with flat ends, and are made of wrought-iron plates, nearly half an inch in thickness. They are 70 feet in length, and 6 feet in diameter. At each extremity is a cast-iron door, flat on the outside, and concave on the inner side, provided with balance-weights for raising and lowering it. Each end is strengthened by five parallel cast-iron girders, whose extremities are held by wrought-iron straps, riveted on to the circumference of the tanks. Notwithstanding the great strength of these girders, several were broken by the pressure applied during the process. The vessels are lined with felt, upon which is laid a covering of closejointed fir battens, fastened with copper rivets. This precaution is necessary to prevent the mutual deterioration which would arise from the contact of the iron and corrosive sublimate. There was originally only one brass force pump, 2 inches diameter, and 6 inches stroke. This being

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found insufficient, another was added of 4 inches diameter, and henceforward a pressure of 100 lbs. per square inch was easily obtained. The air-pump is 10 inches diameter, and 15 inches stroke. Its construction is of the ordinary kind. The author gives, in an appendix to the paper, a minute description of the various parts of the apparatus, with the details of their dimensions and weight. The process is simple and rapid the corrosive sublimate is first mixed with warm water in a trough, in the proportion of 1 lb. of the former to 2 gallons of the latter; the clear solution is then poured off into the reservoir, where water is added till it is diluted to the proper point, which may be ascertained by a hydrometer. A more perfect test is the action of the solution upon silver, which it turns brown at the requisite degree of saturation. The operations of exhaustion and pressure employ eight men for five hours, the whole process occupying about seven hours, during which time from 17 to 20 loads are kyanized in each tank. It is desirable that the timber should remain stacked for two or three weeks after kyanizing before it is used. It was found that about lb. of corrosive sublimate sufficed to prepare one load (50 cubic feet) of timber. About 337,000 cubic feet of timber were kyanized, the average expense of which, including part of the first cost of the tanks, was about 5d. per cube foot. The timber was tested after the process, and it was found that the solution had penetrated to the heart of the logs.

The paper contains some interesting tables, exhibiting the quantity of solution taken up by different kinds of wood, with and without exhaustion. From these it appears that the saturation per cube foot, in the latter case, did not exceed 2.25 lbs. with specimens of Dantzic timber; whereas it ranged between 12.24 lbs. and 15.25 lbs. with pieces of home-grown wood. The author observes that this striking difference may be partly due to the greater compactness of the foreign timber.

Appended to this communication is a correspondence between Mr. J. G. Lynde and Mr. James Simpson relative to the best tests of the presence of corrosive sublimate, accompanied by letters from Mr. Colthurst and Dr. Reid. The former of these describes the process of kyanizing adopted on the Great Western Railway, and the latter suggests the three following tests: 1st, Dilute hydro-sulphuret of ammonia; 2nd, A strong solution of potassa; dilute nitric acid and proto-muriate of tin, also gold-leaf with this solution; and 3rd, Iodide of potassium. Directions are given for the application of these tests.

Mr. Lynde also mentions the use of a solution of nitric acid; and, by the application of hydriodate of potash detecting the presence of mercury in a specimen taken from the heart of a log of timber 10 inches by 5 inches and 9 feet long. He also details appearances of the destructive action of the corrosive sublimate upon the iron-work with which it came into contact, which would be prejudicial to the use of iron bolts in kyanized sleepers.

A drawing, explanatory of the whole apparatus, accompanied the communication.

In answer to questions relative to the process of exhausting the air from the receiver in which the bank-note paper was wetted at the Banks of England and Ireland previously to being printed, Mr. Oldham stated that as an experiment a packet of 1000 sheets of paper had remained a whole day in water without being wetted through; whereas, by exhausting the air from the vessel containing them, to a partial vacuum of 22 inches of the barometer, and admitting water, they had been perfectly saturated in five minutes. The edges of the paper, in simple immersion, would rot away before the mass was saturated by the exhausting process 5000 sheets of bank-note paper would absorb 16lbs. of water.

Mr. Simpson conceived that exhaustion would facilitate the process of kyanizing; but he believed that if time was allowed, pressure would accomplish the same end as perfectly; for he had observed that pieces of wood which had remained four or five days in a water-main, under pressure, had become perfectly saturated. Captain Scoresby, in his account of the whale-fishery, remarks that when a whale carries a boat down it rarely rises again, most probably because the fish plunges to such a depth that the extreme pressure waterlogs the boat. Instances had been known of the specific gravity of the planking being doubled by being carried down.

Mr. Newton remarked, that immersion of timber in close tanks had been practised by Mr. Langton many years since, for bending timber. A boiling fluid was used in the tanks, and the wood was subjected to heat for a considerable period. He had understood that Mr. Newmarch, of Cheltenham, was the first person who used corrosive sublimate for preserving timber, and that he had prepared and employed considerable quantities of wood. Mr. Kyan subsequently revived the system.

In Mr. Oldham's process of wetting paper pressure was not requisite, on account of its

open texture. About the year 1819, Mr. Oldham had tried the same process with perfect success for preserving meat,

Exhaustion had been tried by Mr. Harris for cleansing wool. The cops of wool were put into an exhausted receiver; a solution of an alkali was then admitted. After remaining a short time in the liquid, a sufficient quantity of diluted acid was added to neutralize the alkali, and the wool was washed out in clean water. The process succeeded perfectly, but was too expensive.

Mr. Palmer had employed the kyanizing process for large pieces of timber, for the ribs of lock-gates, but had no means of ascertaining the depth to which the mercury had penetrated. The use of corrosive sublimate was first suggested by Sir H. Davy, in his lectures at the Royal Institution, as a means of destroying the vegetating process in timber, by the combination of the chlorine in the former with the albumen of the latter. Mr. Palmer much doubted whether the means used for exhausting the capillary tubes effected the object, unless the timber was in a dry state; and he considered it equally doubtful whether the solution could be forced to any considerable depth by compression, especially if any moisture actually filled the capillary tubes. The application of pressure in the process of salting meat, suggested by Mr. Perkins many years ago, was a complete failure.

Mr. Simpson observed, that in the experiments of Messrs. Donkin and Bramah, pressure alone had been used, and it could easily be understood that owing to the cellular formation of meat, the pressure, instead of forcing the salt through it, caused the substance to collapse, and the brine was prevented from penetrating.

Mr. Braithwaite explained that in Payne and Elmore's process, although pressure had been found indispensable, the meat was more perfectly prepared when exhaustion was also employed, therefore both were now combined.

Mr. May reverted to the subject of kyanizing timber; he believed that exhausting the air from the tanks previously to the admission of the solution was a loss of time-the fluid should be admitted first, or at least while the exhaustion was proceeding; labour and time would thus be saved, and the air would be more completely expelled from the capillary tubes before pressure was applied. It was essential that the timber should be as far as possible deprived of its sap as well as dried: as either sap or moisture appeared to prevent the proper action of the corrosive sublimate.

Mr. Cubitt regretted that experiments had not been made on the same kinds of wood, both with and without exhaustion. The experiments on small pieces of foreign (Memel and Dantzic) timber with 80lbs. to

PRESERVATION OF TIMBER.

100lbs. pressure without exhaustion, showed an increase of weight of from 14 to 2oz. in pieces of about th part the size of a sleeper, and that result agreed very nearly with his practice with sleepers of Memel and Dantzic timber, when kyanized without exhaustion under a pressure of 80lbs. to the inch; sleepers of 24 to 23 cube feet, gaining from 3lbs. to 5lbs. in weight by the process. No result had been given of experiments with sleepers of foreign fir timber in which both exhaustion and pressure had been applied, but it appeared that the Scotch fir sleepers weighing 100 lbs. when kyanized under exhaustion and a pressure of 100lbs. to the inch, gained 33 per cent. in weight, which was equal to three gallons of water being forced into less than 3 cube feet of timber; he thought that this difference could not be all due to exhaustion, but that it must depend greatly upon the quality of the wood, because under a pressure of 100lbs. to the inch, the air contained in a tubular substance (such as fir timber) would all be compressed into about 4th of its natural bulk, without previous exhaustion, so that the difference between 5lbs. and 30lbs. forced into a sleeper, could not, he thought, be all due to exhaustion, but must depend upon other circumstances not explained in this paper.

The President thought that the greater degree of absorption by the Scotch fir might be accounted for by its open texture, whereas the foreign timber was more compact, and also contained more turpentine. It might also have been wetter than the Scotch fir, which he believed had been the case.

Mr. Taylor observed, that hitherto the attention of the meeting had been entirely directed to mechanical action, but that the chemical combination of the corrosive sublimate with the albumen of the wood, was the point most insisted upon by Kyan; it was supposed to be similar to the operation of tanning hides, in which the tannin of the bark combined with and saturated the animal gelatin, which would not otherwise be permeable by the fluid in which it was placed.

Lieut. Oldfield suggested that if the timber when piled in the tank was subjected to the action of heat at 212°, the moisture contained in the capillary tubes would be expelled in the form of steam, and that on the admission of the solution, the tubes would instantly be filled with it, because of the partial vacuum formed in them.

Mr. Colthurst observed, with regard to the tests for ascertaining the amount of saturation of the timber, that he had tried all those described by Mr. Lynde, and had not been able to discover the presence of mer

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cury in the heart of any of the timbers prepared for the Great Western Railway; their dimensions were 6 inches by 12 inches; Dr. Faraday had, he believed, detected it by the aid of the galvanic battery in the heart of a piece of timber 2 feet square, after simple immersion in the solution for fourteen days.

Mr. Moss had tried many experiments as to the most delicate tests for ascertaining the depth to which the mercury had penetrated; the most satisfactory test was gold leaf, as from its strong affinity for mercury, the presence of the latter was immediately detected. The mode of proceeding was to put some fibres of the wood to be tested into a small test tube, mixed with a portion of dry carbonate of soda; then, to place over, but not in contact with it, a small piece of gold leaf, and apply heat to the bottom of the tube. If any mercury was present, in however small a quantity, the fumes would rise and discolour the gold leaf.

Mr. W. Cubitt said, that timber was at all times, more or less, charged with moisture he had found deals, supposed to be dry, lose 10 per cent. of their weight from steam drying; it was evident that the presence of moisture in the pores of the wood must militate against the success of kyanizing by simple immersion, unless it was continued for a very long period. In close tanks, when exhaustion and pressure were resorted to, the moisture was perhaps of less importance, but still, if the sap was extracted, and the timber previously dried, the process of kyanizing would be more efficient.

Mr. S. Seaward adopted Mr. Palmer's position, as to the almost impossibility of forcing the solution through the capillary tubes of a long piece of timber, the pressure being applied equally all over the surface : he believed the present method of kyanizing to be very imperfect, and alluded to a number of sleepers so prepared for the West India Dock warehouses having been recently discovered to be decayed.

Mr. Martin confirmed this account of the decay of the sleepers: fifty out of seventy were destroyed; they had been prepared by simple immersion, and had been down about five years. He had understood that some of the wooden tanks in which the solution was kept at the Anti-Dry-Rot Company's yard were decayed.

Mr. C. May believed that the destruction of the tanks might have arisen from the constant corrosive action of the mercury, and not from decay. The capillary vessels of timber being filled with air and sap, under exhaustion the air would expand and drive before it a considerable portion of the sap and moisture. In preparing the compressed trenails and wedges he used steam,

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