PORTLAND BEDS. 



339 



building-purposes, etc. The Curf is, in places, a hard and sometimes oolitic 

 limestone with much flint or chert, which separates the two beds of freestone. In 

 it occur many specimens of Ammonites gigaiiteus. The Roach is an oolitic shell- 



FiG. 51. — Section of Strata, Isle of Portland. 

 (H. W, Bristow.) 



i-'.'.-i'-;^;';'. ^ 



ft. in. 



I o Soil. 



10 o Rubble, clay, and tbin-bedded lime- 

 stone. Hai'd Slatt. 



2 Clay. [sand. Bacon Tier. 



1 9 Earthy limestone with layers of 



3 Clay. 



2 3 Soft earthy limestone. Aish. 



1 6 Sandy and cherty stone. Soft Biiri: 

 I o Great Dirt-bed or Black Diri. 



g o Compact Limestone. Tc>J> cap. 



o 4 Dirt bed. 



2 6 Compact limestone. Skull Cap. 



3 6 Oolitic shell -limestone. Roach. 



8 6 Oolite. WhU Bed. 



Cherty bands, etc. Curf atid Flint. 



8 6 Oolite. Base Bed. 



40 9 Limestone, false-bedded in places, 

 with bands of chert. 



o Blue marl and sand with nodules of 

 cement-stone. 



limestone, containing casts of Ceriihium Portlandicum, Trigoitia, etc. ; it merges 

 into the Whit Bed. It has been used in the construction of Harbours, Break- 

 waters, Piers, etc., but as a rule is not removed from the Quarries. The Whit and 



