MIKING AND MINERAL PRODUCTS.

INTRODUCTION.

The objects placed in this position are so in consequence either of their size, or of their peculiar fitness for sucha site. On the southern side of the Western Entrance the objects are principally those which belong to Classes1 and 27. Among these are fine specimens of the mineral fuel forming so valuable a feature in the geology ofthis country Several of the blocks of coal have been raised from deep pits by the ordinary lifting tackle,and present, from their size, a favourable idea of the mechanical facilities of extraction and means of transportpossessed by the miners and railroads of England. The blocks of granite, of slate, of serpentine, of stone forgrindstones, and of artificial cement, will likewise attract due notice. On the northern side of the WestEntrance are large anchors, as those used in the Navy, a fine column of granite, specimens of colossal earthen-ware, life-boats, the atmospheric recorder, hothouses, &c. The space within the Building, occupied by any ofthese articles, -would have been great, while their intrinsic attractiveness might scarcely have been adequate toit. In their present position they are also better placed for examination.—R. E.

WESTERN END.

1 Organ, John, Penzance , Cornwall — Manufacturer.

Large block of serpentine from the Lizard, partly

polished.

[The serpentine of Cornwall is a green mineral, passinginto yellow and red, the colour being often veined,spotted, dotted, and clouded. It is soft in the quarry,but becomes hard on exposure, and cuts readily, but itsfracture is irregular. It is soft to the touch, but notgreasy like steatite or talc; is indented by a blow of ahammer ; is infusible before the blowpipe; but partswith water by calcination, and hardens by exposure toheat. It is slightly acted on by acids.

As a rock, serpentine is often mixed with other minerals,so that different specimens do not yield the same result°n analysis. It usually contains, when pure, silica 42 to44, magnesia 36 to 38, water 12 to 13, and is therefore asilicate of magnesia. Its colour is due to oxide ofchromium, but it contains often much iron, and is some-times magnetic.

The serpentine of Cornwall is considered to exhibitfour varieties, differing much in hardness—these arecalled precious, common, steatitic, and calcareous; butthe best kinds for ornamental purposes on a large scaleare those found at Kennack Cove, the Balk, and Cadg-with, where large blocks can be obtained. The blockplaced outside the Building near the south-western exitwill show the magnitude and capability of such blocks.

A considerable quantity of the serpentine of the Lizardwas formerly shipped to Bristol, for the manufacture ofcarbonate of magnesia.—D. T. A.]

2 Board, —, (Agent, James O’Donohue, 5 Quickset

Row, New Road),

Two figures in artificial stone.

3 Teagle, R. & W., 42 Hertford Street , Chelsea —Inventors and Manufacturers.

A figure of Lazarus, in artificial stone ; cast takenfrom a carved wood figure.

4 Raysdale, W.—Producer.

Blocks of gypsum used in the manufacture of plaster.

5 Robins, Aspdin, & Cox, Northfleet , and GreatScotland Yard, Whitehall —Manufacturers.

Slab of Portland cement. Iron te3ting-socket, forproving the strength of the cement. Bricks cementedtogether, equal to a pressure of three tons on the firstbrick. Beam of cement. Bricks, joined together withone portion of cement and four of sand. Step of Port-land cement. Block of cement, which bore a pressure ofupwards of 250 tons, tested by Bramah ’s hydraulic press.Similar block, one portion of cement, and four of sand,which bore a pressure of 120 tons. Block of Portlandstone of like dimensions, which broke under pressure.Brick beam, one portion of cement and three of sand;sustaining a weight of 3$ tons. Bricks, joined togetherwith one portion of cement, and three of sand, bearing aweight of one ton. Blocks of the hardest Yorkshire stone, joined by one portion of cement, and one ofsand, sustaining a weight of three tons.

[Portland cement is formed by calcining together lime-stone and some argillaceous earth, the result being a masswhich rapidly absorbs a certain quantity of water, andthen becomes solid, as a hydrous silicate of lime. Theadvantages over natural hydraulic limes consist generallyof greater hardness and durability, arising from themixture of material being more perfectly under com-mand.—1>. T. A.]