Reports & Proceedings — Liverpool Geological Society. 137 



were obtained from the Edmunds formation of Washington County, 

 Maine, and include: Spirifer (? Delthyris) trescotti, S. cobscooki, 

 S. edmundsi, S. (cf. Cyrtina) lubecensis. 



REPORTS .AJtTID PROCEEDIITGS. 



I. — Liverpool Geological Society, 



January 9, 1917.— J. R. Milton, F.G.S., F.L.S., President, in the 



Chair. 



The following paper was read : — 



"The Millstone Grit of Yorkshire." By Albert Gilligan, B.Sc, 

 F.G.S. 



The petrography of this great series of rocks has been almost 

 entirely neglected since the classic work of Dr. Sorby, carried out in 

 the middle of last century. From the evidence of the pebbles found 

 in the grit beds, Sorby concluded that the material making up the 

 series had been derived from a landmass having the same lithological 

 characters as the Scandinavian Peninsula, which probably formed an 

 extension of that peninsula to the south-west. 



For many years Mr. Gilligan has been engaged in examining not 

 only the pebbles but also the general material making up the series, 

 and has further made a study of the heavy minerals of a large number 

 of the beds. Among the larger pebbles have been found quartz and 

 felspar porphyries, granites of various types, gneisses, schists, sand- 

 stones, and mudstones. The source of some of these can be traced 

 to Scotland, while one of them so much resembles the well-known 

 rhomb-porphyry of the Christiania region as to suggest that it represents 

 one of the facies of that rock. Quartz pebbles are abundant in all 

 the coarser beds, and these invariably show the effects of pressure, 

 many presenting a mylonized structure. The pink felspar pebbles 

 are always exceedingly fresh, and in nearly all cases are found to be 

 microcline or microcline-microperthite. Pieces of pegmatite, the 

 constituents being quartz and microcline, are common in all the beds, 

 but most abundant in the Kinder Scout and Bough Bock. A few 

 small pebbles of great rarity show oolitic structure, while others 

 contain traces of organisms such as sponge spicules, etc. Chert 

 pebbles differing from those specimens which have been examined 

 from the underlying Carboniferous beds have been obtained from the 

 coarse beds. 



The heavy minerals are very irregularly distributed, some layers 

 being extremely rich, while an adjacent bed will yield but a small 

 number. They include the following : ilmenite, magnetite, garnet, 

 zircon, rutile, tourmaline (blue and brown), anatase, and monazite. 

 This last mineral is of great interest, and was first found in the 

 garnetiferous layers of the Bough Bock, and has since been discovered 

 in the basement grit of Pen-y-gent and the Middle Grits of the 

 Aire Valley. 



The Millstone Grit shows such striking resemblances to the Torridon 

 Sandstone that Mr. Gilligan is disposed to think that they were in 

 great part derived from a common source. 



