XIV. 



LIME AND IRON CARBONATES: 



397 



as in Northamptonshire, they exhibit near the surface the rugged 

 appearance of half-empty iron boxes, laminated nodules, and con- 



Diagram CXCV. Grains of Bath oolite, collected round various objects, 

 all immersed in a paste of calcite. 



tinuous beds. In thinner masses, as at Worton, curved and con- 

 centrically-laminated portions of much richness exhibit oolitic 

 grains. Sometimes merely irregular patches diversify the ordinary 

 oolite, as in the upper beds of Great oolite at Stow-Nine-Churches. 



The sandy parts of the series are always found to be in very 

 fine grain ' sea-sand/ as the workmen call it and being often the 

 channel of subterranean water, it is ' quicksand/ as the engineers 

 found on the North- Western Railway. A crystalline web of calcite 

 is occasionally found to unite the grains into a hard rock. 



The clays of the Bath oolitic series are usually blue, and fit 

 for making bricks; those which divide the middle parts of the 

 Great oolite and Inferior oolite are rather marls than clays. The 

 clays above the Great oolite have an estuarine character, at least 

 in part, and contain often jet and rarely cyrenae. Septaria are 

 not usually found in any of these clays. 



The aggregation of these calcareous, arenaceous, argillaceous, 

 and ferruginous elements into laminae and beds is in some respects 

 peculiar. The ' ragstones/ often found toward the top and toward 

 the bottom of thick oolite, themselves shelly or oolitic in texture, 



