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‘C LASS 1 .— MINING- AND MINERAL PRODUCTS.South Side—Areas S. 1 to S. 27.
[United
for common purposes. In its raw state it is a stonecolour, and is used for houses, glass-houses, &c. Whencalcined, it is of a deep brown colour, and is used forfacia, iron-work, &c.; it has a strong grit, and requiresthe use of machinery to pulverize, grind, and prepare it.
129 Fahie, J. K., Tipperary, Ireland —Producer.
White and black clay. Draining tiles and pipes.Felspar , from Cork.
129a Cooper, S.—Producer.
Specimens of drain pipes from the river Shannon.
130 White, John Bazley, k Sons, Westminster —Manufacturers.
Case, containing specimens of cement stones andthose producing plaster of Paris , as used in England forbuilding purposes; showing the raw stone, the powder.calcined and ground, and cubes of cement in a set state.There are two kinds of cement stones: of each kind, aswell as the gypsums, it may be well to say a few words.
1st. Natural cement stones. These include the Sheppeystone (Kent), and the Harwich stone (Essex), which pro-duce different varieties of the cement known as Romancement, introduced by Dr. Parker about 50 years ago.These are both from the older tertiary deposits, and soalso are the Hampshire cement stones found at Christ-church, Romsey , &c., which produce the Medina ce-ment. The Whitby stone (Yorkshire ), is found in thelias formation, the cement produced being known asAtkinson’s cement. At Wolverhampton and in Derby-shire cement stones occur in connection with iron-stone,which imparts to them a ferruginous tint. At Weymouth (Dorsetshire ) similar materials are obtained from theKimmeridge clay, but these are not extensively used forbuilding purposes. Other districts yield natural cementstones, but the above mentioned are those most known incommerce: they are used very largely, both as mortarsand stuccoes.
2nd. Artificial cements:—Portland cement is composedof carbonate of lime and the argillaceous deposit of theMedway and other river3. These materials produce acement of superior quality, both as to strength and colour.A large panel on a wall, representing a Roman Doricwindow opening, shows the colour of this cement, andits adaptation for external stucco. In illustration ofits strength as a connecting material between bricks,stone, &c., are shown:—abeam of brickwork, loaded witha heavy weight, indicating the value of bond courses ofbrickwork in cement, and the. resistance they opposeto superincumbent weight and cross strain. A beam oftiles bedded in Portland cement, adapted for flooring pur-poses. Cubes of stone connected by Portland cement,showing its adhesive power as great in stone as in brick.Bricks made of Portland cement, to test its resistance totensile force. Blocks of Portland cement which have beensubjected to hydraulic pressure, to prove its resistanceto compression. Portland cement combines with gravel,rubble-stone, &c., to form excellent concrete or beton;specimens are to be seen in parts of a block in concretestone made at the Digue of Cherbourg , under the dfrec-dion of Mons. l’lngdnieur Reibell; size of blocks, 15ft. by8ft. by 6ft.; weight, 45 tons; specimen two years old.Part of a block made at Dover Harbour works, underthe direction of James Walker, Esq., which has beenexposed during three years in an isolated position to theaction of the sea and shingle. Parted a block of concretestone, made at Alderney harbour works; composition,1 part cement to 10 parts gravel; weight of blocks 4 to 6tons. Part of a block of concrete stone, 2 years old; thecement was used in a liquid state.
Gypsums , or sulphates of lime, are found in many partsof England, particularly Derbyshire, Nottinghamshire ,and Cumberland; and when calcined and ground theyproduce the material known in commerce as plaster ofParis ; and in combination with alum they produce thehard artificial cements known as Keene’s, Martin’s, and
Parian patent cements. Keene’s cement is composed ofsulphate of lime and alum; the intimate chemical combi-nation of these materials effected by calcination imparts tothe stuccoes made from them, extreme hardness, by whichthey are adapted for use in those parts of buildings wherestrength and durability are required, such as skirtings,columns, pilasters, and mouldings of all sorts; and theyare not liable to be injured by fire, vermin, &c. Asspecimens of Keene’s cement are shown —• a skirtingmoulding, worked in the common quality of Keene’scement; two pavements, of which the ground is the com-mon quality, and the inlaid borders of the finer quality;large panel on wall, second quality, adapted for painting.Specimens, showing that in combination with colours,brilliant and forcible imitations of marbles, granites, &c.,may be produced, the effect being aided by gilding andinlaying; large panel on wall, and pavement, illustratingthe effect of colouring in this material, and its applicabilityto inlaid work, after the style of Florentine mosaic, at acost not much exceeding the price of polished vein marble.
[There are three very different processes of manufacturein the case of hydraulic cements and artificial stone, the oneconsisting of an admixture of caustic lime (with or withoutmagnesia) with silica in a gelatinous state, thus producingin the final result a hydrous silicate of lime; a second,consisting of sulphates of lime burnt with alum; and theother, composed entirely of silica, and forming, in fact,a kind of glass. Each class of artificial stones will be foundnoted in describing the objects exhibited by different per-sons. The hydrous silicates of lime, manufactured arti-ficially, consist, as noticed above, of carbonate of limemixed with argillaceous earth, and calcined with sand orpowdered flint, when the alkali, acting on the silica ata bright red heat, produces a mass which, with the sub-sequent addition of water, becomes permanently solid.—D. T. A.]
130a Piper, T. & W., and White & Sons —Importersand Manufacturers.
Wall panel executed in French plaster, showing its ap-plication as a hard and quick-setting internal stucco inplace of lime rendering.
131 Blyth & Jacobs, 44 Baldwin’s Gardens , Gray’s InnLane, Holborn —Manufacturers.
Gypsum dug from the pits; calcined, and prepared formanure. Specimens of plaster of Paris , with a collectionof articles in the same.
[Gypsum (hydrous sulphate of lime) occurs in variousways and various places very abundantly. In a semi-crystalline form it is called alabaster, and in crystalsselenite. In the same combination without water, it iscalled anhydrite.
Most of the gypsum used in the manufacture of plasterof Paris is obtained from tertiary deposits, of whichenormous masses exist in the neighbourhood of Paris ,especially at the heights of Montmartre . This stone con-tains above 74 per cent, carbonate of lime, and 3 per cent,clay, which greatly improves the strength of the cementmade from it. It lies between marly beds, and is of fresh-water origin; but other beds equally extensive are of thetriassic series occurring with common salt, and othersagain in the oolites of the Alps.
Large quantities of gypsum are obtained from Lincoln-shire (Newark) and also from Derbyshire —the best fromthe latter place.
The gypsum, heated from 250° to 270° Faht., parts withthe whole of its water, and is changed into an anhydroussulphate. In this state it is reduced to a fine powder,and then, on being again mixed with water, becomeswarm, and rapidly solidifies. This is not the case, how-