10 THE NATURAL HISTORY 



and finer grain than Portland ; and rooms are floored 

 with it; but it proves rather too soft for this purpose. It 

 is a freestone, cutting in all directions ; yet has something 

 of a grain parallel with the horizon, and therefore should 

 not be surbedded, but laid in the same position that it 

 grows in the quarry.^ On the ground abroad this fire- 

 stone will not succeed for pavements, because, probably, 

 some degree of saltness prevailing within it, the rain tears 

 the slabs to pieces.^ Though this stone is too hard to be 

 acted on by vinegar ; yet both the white part, and even the 

 blue rag, ferments strongly in mineral acids. Though the 

 white stone will not bear wet, yet in every quarry at 

 intervals there are thin strata of blue rag, which resist rain 

 and frost ; and are excellent for pitching of stables, paths 

 and courts, and for building of dry walls against banks ; a 

 valuable species of fencing, much in use in this village, and 

 for mending of roads. This rag is rugged and stubborn, 

 and will not hew to a smooth face ; but is very durable : 

 yet, as these strata are shallow and lie deep, large quantities 

 cannot be procured but at considerable expense. Among 

 the blue rags turn up some blocks tinged with a stain of 

 yellow or rust colour, which seem to be nearly as lasting as 

 the blue ; and every now and then balls of a friable sub- 

 stance, like rust of iron, called rust balls. 



In Wolmer Forest I see but one sort of stone, called by 

 the workmen sand, or forest-stone. This is generally of 

 the colour of rusty iron, and might probably be worked as 

 iron ore ; is very hard and heavy, and of a firm, compact 

 texture, and composed of a small roundish crystalline 

 grit, cemented together by a brown, terrene, ferruginous 

 matter ; will not cut without difficulty, nor easily strike 

 fire with steel. Being often found in broad flat pieces, it 

 makes good pavement for paths about houses, never 



^ To surbed stone is to set it edgewise, contrary to the posture it had 

 in the quarry, says Dr. Plot, Oxfordsh. p. 77. But surbedding does not 

 succeed in our dry walls ; neither do we use it so in ovens, though he 

 says it is best for Teynton stone. 



2 " Firestone is full of salts, and has no sulphur : must be close grained, 

 and have no interstices. Nothing supports fire like salts ; saltstone perishes 

 exposed to wet and frost." Plot's Staff, p. 152. 



