part -f] THE MILLSTONE GEIT OF YORKSHIRE. 269 



(e) Shales (arenaceous) : tliese yield — zircons, garnets, rutile, tourma- 

 line, leucoxene. 



(/) Shales (micaceous) : these yield — zircons, rutile, garnets, tourma- 

 line, leucoxene. 



The position in the list of minerals gives an indication of the 

 relative abundance, the first-named being most plentiful. 



It will be seen from this that the finer-grained the beds are, 

 the more important become zircon and rutile. 



(2) Succession of beds examined. — For the purpose of 

 this synopsis it will be unadvisable to enumerate every bed, as 

 the localities are given in the table (p. 270), but I simply divide 

 the series into Lower, Middle, and Upper : the Lower to include 

 all beds below the Leathley Sandstone of the 1-inch Geological 

 Survey Map, Sheet 92 (Skipton ), to the top of the Yoredale Shales 

 and Limestones of Ingleborough, Penygent. Fountains Fell, etc. ; 

 the Middle division includes all beds from the Leathley Sandstone 

 to, but not including, the Flags at the base of the Rough Rock, as 

 shown on the map mentioned above; and the remaining Upper 

 division all beds up to the Lower Coal Measures seen resting upon 

 the Rough Rock at Whitehall Quarries, Butcher Hill, Horsforth. 



(a) Lower Division. — Coarse beds (all conglomerates, grits, sand- 

 stones) contain garnets, ilmenite and leucoxene, zircon, tourmaline, 

 rutile. monazite, magnetite. Fine beds (shales) contain zircons, rutile, 

 garnets, tourmaline. 



(b) Middle Division. — Coarse beds (grits and sandstones) contain 

 zircons, rutile, garnets, tourmaline, ilmenite and leucoxene, magnetite, 

 monazite. Fine beds (shales) contain zircons, rutile, tourmaline, garnets. 

 It must be stated here that in some of the separations made from the 

 shales of Otley Chevin almost piu*e cultures of zircon were obtained, only 

 a few grains and particles of rutile and tourmaline being present. 



(c) Upper Division. — Coarse beds (grits and conglomerates) contain 

 garnets, ilmenite and leucoxene, zircon, rutile, tourmaline, monazite, 

 magnetite. Flags at the base of the Rough Rock contain zircons, 

 rutile, garnets, tourmaline. 



The striking fact which appears evident from this enumeration is 

 that the heavy-mineral contents of the Lower and Upper divisions, 

 so far as the coarse beds are concerned, are similar; while, in the 

 Middle division, the garnets, which are the dominant mineral species 

 in the other two, become subordinate to zircon and rutile. 



The tine beds all through show very little differences, zircons 

 being the most plentiful in them all. 



Only two beds of shale of marine origin and yielding marine 

 fossils have been examined. These were of the usual intense black, 

 and exceedingly line-grained. The only heavy minerals found 

 were rhombohedral carbonates (presumed to be calcite), one or two 

 grains of sulphide of iron, and one very small zircon. 



It becomes quite clear from the results recorded above thai 

 the evidence yielded by the investigation of the included pebbles 

 and the coarser material is borne out in an interesting manner 

 by the presence of such heavy minerals as those described. 



