Vol. 70.] OF DURHAM MAGNESIAS LIMESTONES. 245 



LIII. The calcareous investing matrix, removed by washing the 

 powder from it. 



LIV. The Lower Limestone underlying the above beds. A 

 yellow, thinly-bedded, compact, rather fissile rock. No definite 

 fossils. 



LI. 



Insoluble residue 2*31 



Fe 2 3 , etc 0-46 



CaC0 3 54-66 



MgC0 3 43-06 



Totals 100-49 



LII. 



2-55 



0-41 



53-15 



44-46 



LIII. 



2-69 



0-78 

 81-88 

 15-50 



LIV. 



0-43 



0-83 

 55-17 

 44-37 



100-57 



100-85 



100-80 



0-22 

 97-39 



63-43 

 33-95 



2-35 

 97-19 



Calcite 3'40 



Dolomite 94*32 



Coast-section near Horden Burn. — A patch of original 

 rock about 20 feet thick, extending for 70 yards at the base 

 of the cliff. It underlies 40 feet of calcareous breccias, and at 

 the southern end graduates into the calcareous beds. The first 

 sign of alteration is the infilling of the empty stellate spaces with 

 calcite, and the development of incoherent powdery material with 

 obliteration of the original rock-structure. Then incipient spongy 

 calcareous structures begin to appear in the bedded rock, and the 

 powder becomes washed out. No fossils seen. 



LV. Fine-grained, soft, white, well-bedded, ' soapy ' rock, full of 

 clean cavities arranged in stellate aggregates, with very small 

 lenticular cavities. 



LVI. Fine-grained, yellow, fetid, ' soapy ' rock without cavities. 

 It is massive in part, and closely associated with the above. 



LVII. Hard segregated material, developed in the above rocks 

 towards the southern end of the section. 



LV. 



Insoluble residue 1*99 



Fe 2 3 ,etc 0-38 



CaC0 3 53-13 



MgC0 3 44-24 



LVI. 



3-14 



0-61 



52-80 



43-86 



LVII, 



2-35 

 0-26 



82-86 

 14-58 



100-41 



100-05 



0-58 

 96-08 



65-50 

 31-94 



Totals 99-74 



Calcite 0-46 



Dolomite 96-91 



Bedded Middle Series, on the Western side of the 

 Shell-Limestone. 



These beds, owing to greater denudation in the north, are con- 

 fined to the south-western portion of the Durham Permian, where 

 they cover a considerable extent of country. They are nearly 



