LIMESTONES OE SOUTH DEVON. 383 



Percentage. 



(a) Hopes Nose Limestones. 



Oalceola Limestone 1 13"5 



2 18-6 



Below the Coral Limestone 1*1 



Coi-al Limestone 2*0 



Above the latter 3-5 



(b) Baddy Hole Limestones. 



Base of Quarry 0"6 



Other residues in ascending order : l^o. 1 0"6 



Ko. 2 1-6 



iS^o. 3 20 



A^o. 4 3-4 



No. 5 3-5 



Top of Quarry, No, 6 3*3 



(c) Lummaton Limestones: No. 1 ' 0"6 



No. 2 0-2 



(d) Barton Limestones: No. 1 2*0 



No.2 2-9 



No. 3 0-2 



(e) Dunscomhe Limestones. 



Main mass, below the Grouiatite Beds 1*8 



Goniatite Limestone 10-2 



The most noticeable feature in the above table is the small per- 

 centage of residue in the Lummaton Limestones, and the variable 

 nature of the Barton rock. But the detailed examination of the 

 residues, which now follows, shows that the small amount at 

 present existing is no guide to what may have been originally 

 deposited — because of the decomposition which has taken place. 



I have already referred to the Goniatite Limestone as exhibiting 

 structural differences compared with the beds below, a fact further 

 illustrated by the high proportion of residue which the Goniatite 

 Limestone contains. 



§ 5. Detailed examination op the Residues. 



(a) Hope's Nose Limestone Residaes. — Commencing with the 

 lowest beds exposed in the quarry, I find the residue to consist of a 

 very fine, light grey material, and a further quantity of heavier 

 material. 



The very fine portion is made up of small flakes of mica, quarti^ 

 grains, and rutile ; there also occur incipient micro-crystals of 

 quartz, microlites, and a quantity of very minute crystals resem- 

 bling, in some respects, the clay-slate needles of rutile. These 

 minute crystals are a great puzzle ; they occur in numbers so vast 

 as to become an important feature and cannot be passed over. 

 Being in doubt as to the nature of these objects, I propose, for 

 the present, to refer to them as microlitic needles. They occur 

 sometimes in aggregates and then appear to be associated with 

 decomposing mineral fragments ; sometimes they occur singly in 

 great numbers. 



The material of greater specific gravity includes aggregates of 

 micro-crystals of quartz, cryptocrystalline siliceous flakes, and 

 micas. The siliceous flakes, and apparently some of the micas, 



2e2 



