250 



Dr. J. A. Smythe — Inclusions in 



slight. This is clearly the material which gives the crystallization- 

 phenomena of the mould-surfaces. 



The occurrence of concentric inclusions, noted above, is borne out 

 by the sections. In one prominent example the inner inclusion is 

 largely made up of spherulites, while the material of the enveloping 

 inclusion is of greater variety and shows a more advanced stage 

 of crystallization. 



Mention may be made here of some smooth, roundish masses which 

 occur along with the inclusions, and differ from them externally in 

 the absence of bright facets and films and by a slight, but distinct, 

 surface-sheen. Sections of these have all the characters of the 

 inclusions proper, and, in some cases, actually enclose them. Though 

 distributed sparingly, they evidently belong to the same order of 

 phenomena as the inclusions. 



The Chemistry of the Hocks. 

 For the purposes of chemical examination several inclusions, or, 

 more accurately, their facetted hemispheres, were isolated as com- 

 pletely as possible, and a fairly large sample of the whin immediately 

 surrounding them was also taken. Both samples were coarsely 

 crushed, sieved free from dust, then ground and dried at 110° C. 

 Total iron in each case is reckoned as ferrous oxide. The analytical 

 data are given below in columns I and II, those for the whin being 

 the mean values of closely-agreeing duplicates. Some other analyses 

 (in which the iron is recalculated as ferrous oxide) are given in the 

 table (columns III, IV, and V) for the sake of comparison; they 

 will be dealt with later. 



SiOa 



AI2O3 



TiOa 



FeO 



MnO 



CaO 



MgO 



K2O 



Na2 



P2O5 



CO2 



H2O 



S.G. 



I. 



II. 



III. 



IV. 



V. 



I. 



49-54 

 16-64 

 2-84 

 11-44 

 0-20 

 9-00 

 5-51 

 0-97 

 2-33 

 0-28 

 0-16 

 0-47 



99-38 



2-900 



2-725 2-67-2-70 2-770 



2-810 



Whin Sill surrounding inclusions, Snook Point. 

 Inclusions, Snook Point. 



Felspars from Whin Sill, Caldron Snout (analysis by Teall). 

 Cleveland Dyke (mean of three analyses by Stead and Stock). 

 Acklington Dyke (analysis by Stead). 



The figures for the rock surrounding the inclusions (No. I) agree 

 very closely with Teall's analyses of the Whin Sill from Borcovicus 

 and Caldron Snout,' and they aff ird fresh evidence of the uniformity 



^ Quart. Journ. Geol. Soc, vol. xl, p. 654, 1884. 



