1847.] 



THE CIVIL ENGINEER AND ARCHITECT'S JOURNAL. 



335 



cell of fresh air, or, if necessary, of air tempered for each prisoner, without 

 the iucouvenienceof ilraughls. The extraction from each cell of a quantity of 

 foul air equivalent to the quantity of pure air introduced ; and the carrying 

 CD of the heating and ventilation without facilitating ihe means of com- 

 munication, whether of Bound or otherwise, between the ditl'erent cells." 



IRON VESSELS. 

 The following report of a survey for the purpose of ascertaining the 

 injuries sustained by the Great Britain, has been delivered to Captain 

 Claxton. It clearly shows the superiority of iron over wood for constructing 

 sea-going vessels. 



" We, the undersigned, certify that we have at your request this day 

 been on board the steamer. Great Britain, now lying on Ihe gridiron iu the 

 Prince's Dock Basin, and both inside and out have examined the means 

 adopted by the foreman boiler maker, Mr. John Crew, for stopping the 

 leaks in the bottom of Ihe vessel whilst lying iu Dundrum Bay. We lind 

 the principal holes to have been six in number, varying in dimensions from 

 2 ft. by 12 in. to 5 ft. 9 in. by 16 in. ; and there are oilier formidable holes 

 and cracks of smaller dimensions. From their size and position, under 

 the keel of the ship, we are of opinion that it must have been a work of 

 extreme difficulty to make them in any degree water-tight. We are in- 

 formed that, besides the water in which the ship lay, there was never less 

 than 2i or 3 feet of water and sand in her hold after the damage she sus- 

 tained from the gales in the early part of the winter; and taking this fact 

 into consideration, with the other difficulties that had to be encountered, 

 we are of opinion that the greatest ingenuity and perseverance must have 

 been exercised to stop the holes in such a manner as to enable the vessel 

 to float. The method adopted by Mr. Crew for this purpose was as fol- 

 lows : — A plate of sufficient size was passed edgeways through each hole 

 from the inside, having a screwed bolt attached to it as nearly in the centre 

 as possible. This plate was then adapted to cover the hole on the outside, 

 and was drawn tight up by a screwed nut and crossbar from the inside, 

 being packed with felt to prevent leakage as much as possible. On the 

 whole, as boiler-makers' or iron ship builders' work, we consider it to be a 

 most extraordinary performance, which, regarded from beforehand, must 

 have appeared of almost hopeless execution, and must have been one of 

 the greatest amongst Ihe numerous difficulties over which the energy and 

 determination of the rescuers of this vessel have ultimately triumphed. 

 We do not conceive that it would have been possible, under similar circum- 

 stances, to stop holes of the size mentioned in Ihe bottom of a wooden ves- 

 sel ; and we may further remark, that the iron of which the frames and 

 plates are made must have been of most excellent quality. 



Fawcett, Preston, and Co. 



E. Ross, engineer. 



T. Baker, engineer. 



E. Pargeter, foreman boiler-maker. 



N. Furlong, engineer. 



W. B. M'Allister, foreman boiler-maker. 

 Liverpool, Sept. 2, 1847. 



ARTIFICIAL MINERALS. 



The experiments of M. Ebelmen, to produce minerals artificially, com- 

 municated to the Academy of Sciences, Paris, are thus given in L'Institut: 

 the immediate subject being chiefly the varieties of the ruby. 



" The method I adopted to crystallise these compounds, depended upon 

 the property of boracic acid to dissolve all the metallic oxides, and upon 

 the great volatility of this acid at a high temperature. I thought that by 

 dissolving, in melted boracic acid, alumina and magnesia, mixed in the 

 proportions that constitute the spinel, and by exposing this borate in open 

 vessels to the high temperature of the porcelain kiln, the afUnity of alu- 

 mina for magnesia would determine the separation of a crystallised alunii- 

 nale, and the complete expulsion of the boracic acid. In short, 1 em- 

 ployed boracic acid, at a high temperature, as water is used at ordinary 

 temperatures, to obtain crystallised salts by evaporation alone. The 

 proportions were about one part of melted boracic acid to two parts 

 of alumina and magnesia, mixed synthetically to constitute the compound, 

 AP O^, MgO; with the addition of a small quantity of the bi-chromale of 

 potash. These materials, well mixed, were put on a platinum leaf, in a 

 biscuit-cup, and exposed to the beat of a porcelain biscuit-kiln. I obtained 

 a surface covered with crystalline facets, presenting in their interior reticu- 

 lated cavities, the form of which was easily distinguished with the lens. 

 These crystals were rose coloured, transparent, readily scratching quartz, 

 and presenting the form of regular oclohedrons without any modification, 

 They are quite infusible in the blow-pipe. These characters, joined to Ihe 

 tomposition of the crystals, synthetically ascertained, appear sufficiently 

 conclusive to establish their identity with the spinel. 



" By substituting for the magnesia its equivalent of the protoxide of 

 uanganete, a crystallised product is obtained in large laminae, in the form 

 •f tquilateral triangles, or uf regular bexagoas. These crystals, also, 



readily scratch quartz. I consider them to be the manganesiferous spinel 

 A12 O-'' MnO, which has not jet been met with in the mineral kingdom. 



" Oxide of cobalt, substituted for Ihe magnesia, equivalent for equiva- 

 lent, gave bluish black crystals, regular oclohedrons. 'I hey agaiu scratch 

 quartz, but with more difficulty thau the preceding." 



In employing alumina and glucine iu ihe proportions that constitute 

 cyniophane or chrysoberyl, Al- O^ GIO, a bristling mass of crystalline 

 asperities uf great brilliancy is obtained. This product readily cuts 

 quartz, and very cleanly topaz. It presents then a hardness comparable 

 to the crystallised cymophaue. 



Certain silicates, iotusible at the temperature of our furnaces, appear 

 capable of beiug reproduced by the same process. Thus, in melting the 

 elements of the emerald with half their weight of boracic acid, at the same 

 temperature as in the preceding experiments, a substance is obtained, 

 which easily scratches quartz, and the surface of which presents a great 

 number of facets having the form of regular hexagons. 



" I content myself," M. Ebelmen adds, in conclusion, " with submitting 

 to.day these first indications, hoping, however, soon to present to the Aca- 

 demy a more detailed and more complete work. But 1 am convinced, at 

 present, that it is possible to produce, at temperatures below those of our 

 iron smelting furaaces, diaphanous crystals the hardness and external 

 characters of which are analogous to those of precious stones. It is pro- 

 bable that in repealing these experiments in apparatus of certain dmieu- 

 sions, like reverberating furnaces, by operating on large quantities of ma- 

 terials, and continuing the application of heat sufficiently long, much 

 larger crystals may be produced ihaii those I have obtained, working with 

 a few grammes only. Another conclusion to be drawn from the preceding 

 facts is, that many species of minerals have the power to produce them- 

 selves and crystallise at temperatures much below those necessary to melt 

 them." 



Specimens of the products mentioned in the communication were sub 

 milled to the Academy. — Literanj Gazette. 



NOTES OF THE MONTH. 



French Proof Engravings. — At a recent meeting of the Royal College of 

 Chemistry, Prof. Taylor explained the manner in which French printsellere 

 are enabled to increase the number of proof copies, to the great detriment 

 of the purchasers. He showed that they had adopted the system of giving 

 the paper a slight coating of carbonate of lead, which rendered the iinpres. 

 sion more perfect after the plate had become deteriorated ; but that this was 

 very soon converted into sulphide by the action of sulphuretted hydrogen 

 constantly floating in the atmosphere of large towns, and by which inter- 

 change the print was destroyed. The presence of lead on this paper was 

 showed by experiment. Prof. Taylor then stated that the brown colour of 

 Valenciennes lace was due to a similar cause ; the manufacturers sprinkling 

 it with carbonate of lead, to make it look clear, — which being changed into 

 sulphide on exposure to the air, gave the lace the dingy appearance so much 

 prized by ladies. 



Testjor distinguishing Iron from Steel. — To distinguish iron from steel 

 by a chemical process, take pure nitric acid, dilute it with so much water 

 that it will only feebly act upon the blade of a common table knife. If a 

 drop of the acid thus diluted be suliered to fall upon steel, and allowed to 

 remain upon it for a few minutes, and theu washed off with water, it will 

 leave behind a black spot. But if a drop of this acid be suflered to act 

 upon iron iu the same niauoer, the spot will not be black, but of a whitish- 

 grey colour. The black stain is owing to the conversion of the carbon of 

 the steel into charcoal, which thus becomes predominant; and iron being 

 nearly free from carbon, can produce only a grey stain. The utility of this 

 test is not confined to finished articles manufactured of steel, but its appli- 

 cation enables the workman in iron and steel to ascertain also the quautil; 

 and uniformity ol texture uf unfinished articles. 



Sheathing for French Vessels. — The [Minister of Marine has given orders 

 that several experiments shall be made to test the quality of copper sheath- 

 ing employed in England and France, fur the coppering of vessels, as that 

 at present used in the French Navy and merchant service soon corrodes, 

 as has been proved by the recent report on the state of the bottoms of the 

 steamers, frigates, and other ships of war, where French copper has beea 

 employed instead of British, as hitherto, and will have to be recoppered as 

 soon as the superiority of the one over the other is fully proved. The 

 copper manufactured in France is of a very soft nature, very corrosive, 

 and but little adapted, either lor marine purposes, boilers, or steam-engines, 

 if not mixed with English metal. 



Stagnant Water. — M. Fleurian de Bellevue states, as the result of bis 

 observations and inquiries on the eli'ects arisiug from stagnant water, that 

 in marsh lands which are covered with water to a considerable depth dur- 

 ing the great heats of summer, the inhabitants of the localities in which 

 they exist are not more unhealthy thau in other localities ; but that where 

 the stagnant water is of slight depth the decomposition is attended with 

 frighiful consequences, and the mortality is great. He recommends tbat 

 in all low lands where there is water during the summer of so sligbi a 

 depth as to render decomposition certain, the ishabitiiute should form •*« 



