RAMBLES OF A GEOLOGIST. 373 



into a fire-clay, so altered in the organic pabulum, animal and 

 vegetable, whence it derived its fertility, that, even when laid 

 open for years to the meliorating effects of the weather and 

 the visits of the winged seeds, it will not be found bearing 

 a single spike or leaf of green. But here, in smell at least, 

 that ancient mud, swum over by the Diplopterus and Dipla- 

 canthus, and in which the Coccosteus and Pterichthys bur- 

 rowed, has undergone no change. The soft oose has become 

 solid rock, but its odoriferous qualities have remained unal- 

 tered. I next visited an excavation a few hundred yards on 

 the upper side of the pump-room, in which the gray fetid 

 breccia of the Strath has been quarried for dyke-building, 

 and examined the rock with some degree of care, without, 

 however, detecting in it a single plate or scale. Lying over 

 that Conglomerate member of the system which, rising high 

 in the Knock Farril range, forms the southern boundary of 

 the valley, it occupies the place of the lower ichthyolitic bed, 

 so rich in organisms in various other parts of the country ; 

 but here the bed, after it had been deposited in thin horizon- 

 tal laminse, and had hardened into stone, seems to have been 

 broken up, by some violent movement, into minute sharp- 

 edged fragments, that, without wear or attrition, were again 

 consolidated into the breccia which it now forms. And its 

 ichthyolites, if not previously absorbed, were probably de- 

 stroyed in the convulsion. Detached scales and spines, how- 

 ever, if carefully sought for in the various openings of the 

 valley, might still be found in the original laminae of the 

 fragments. They must have been amazingly abundant in it 

 once ; for so largely saturated is the rock with the organic 

 matter into which they have been resolved, that, when struck 

 by the hammer, the impalpable dust set loose sensibly affects 

 the organs of taste, and appeals very strongly to those of smell. 

 It is through this saturated rock that the mineral springs take 

 their course. Even the surface-waters of the valley, as they 



