SANDSTONES AND FIRE-CLAYS. 183 



their erection has excited so much comment, are built of 

 magnesian limestone; had the sandstones of Fife or Mid- 

 Lothian been adopted, as was at one time proposed, the 

 chisel-marks of the builder would have remained unoblite- 

 rated for centuries. 



Next to the sandstones or freestones of the Coal-measures 

 we may place the FIRE-CLAYS, or those argillaceous beds which, 

 from the peculiarity of their composition, may be baked into 

 fabrics of any shape, and of unsurpassed resistance to the 

 effects of either fire or water. These clays, at one time 

 little sought after, have now become of vast importance, 

 and are largely used as substitutes for stone and iron. 

 Plastic, and capable of being fashioned into any form, they 

 are extensively used for fire-grates, furnace-linings, retorts, 

 sewage - pipes, floorings, architectural mouldings, garden 

 ornaments, and a thousand other purposes affording 

 objects of beauty as well as of utility, and, when properly 

 manufactured, of unconquerable durability. Few manu- 

 factures have come of late years so largely into use as 

 fire-clay fabrics \ and, considering their recent introduction, 

 we may confidently look forward, not only to their rapid 

 extension, but to a skill in manipulation which will rival 

 the finest productions of the potter and sculptor. But, 

 altogether apart from works of art, the use of fire-clay 

 fabrics in furnaces, and above all in the cheap and effi- 

 cient drainage of our towns, has been a boon of no common 

 value, as tending at once to the health, the comfort, and 

 amenity of our densely congregated populations. Of course, 

 as the manufacture of fire-clays is intimately dependent on 

 a cheap supply of fuel, the relation of coal and fire-clay in 

 the same field, and often in the same mine, is a thing that 

 must strike the attention of the least reflecting. 



Even the most worthless -looking beds in the forma- 

 tion the SHALES, or consolidated muds are now rapidly 



