344 MR. H. H. ARNOLD-BEMROSE ON THE GEOLOGY OE [Aug. I 9°3? 



23. Parsley Hay. 



This cutting is in a massive white or light-grey limestone. A 

 thickness of about 66 feet of strata is seen. At the northern end of 

 the cutting the beds dip 10° north-eastward, and contain a few corals. 

 Near the bridge they become horizontal. A brown dolomitized lime- 

 stone occurs in irregular patches, and in vertical vein-like masses. 

 The latter are due to dolomitization of the limestone along vertical 

 joints. A hand-specimen (1096) from a vertical joint shows the 

 junction between the dolomitized and the ordinary limestone. The 

 dolomitized portion is brown, the unaltered part grey. The grey 

 limestone near the junction contains numerous brown spots which 

 consist of rhombohedra of dolomite. 



The middle beds near the northern end of the cutting yield fora- 

 minifera (1097). 



III. Petrography of the Pocks. 



(1) Calcareous Tuff in Newton-Grange Cutting, 



Thin slice 1046 (see p. 339). This is a bluish-grey tuff similar 

 to some parts of the thick bed of tuff in Highway-Close Earn, de- 

 scribed in my previous paper. 1 The irregular outlines and vesicular 

 structure of the lapilli are easily seen in a hand-specimen of the rock. 

 In a thin slice there are many vacant spaces, owing to the lapilli 

 having dropped out in the process of grinding. Some lapilli are, 

 however, left in the thin slice, and are altered to calcite. This rock 

 was originally a calcareous tuff, consisting of vesicular lapilli in a 

 cement of calcite or in a sediment containing calcium- carbonate. 



(2) The Limestones. 

 The limestones may be conveniently divided into : 



(a) Crystalline limestones, either partly or wholly dolomitized. 



(b) Fine-grained limestones, partly crystalline. 



(c) Granular and, in part, oolitic limestones. 



(d) Encrinital limestones. 



(a) Some of the dolomitic limestones consist of a more or 

 less granular aggregate of dolomite and calcite with few, if any, 

 rhombohedral outlines. 



A thin slice (973) from the New-Inns cutting shows clearly- 

 defined rhombohedral crystals of dolomite, with patches of iron- 

 oxide and a few quartz-grains. 



The grey limestone near its junction with the brown dolomitized 

 limestone in the Parsley -Hay cutting (1096) consists of clear crys- 

 talline calcite polarizing in bright tints, in which are embedded 

 idiomorphic rhombohedra and segregations or patches of brown 

 dolomite. 



1 Quart. Journ. Geol. Soc. vol. lv (1899) p. 233. 



