part 1] the mti. i. mom; obit of Yorkshire. 203 



Discussion. 



The SECEETAET read the following remarks, received from 

 Dr. B. N. Peach :— 



' I had the opportunity of reading- the Author's MS. on ' The Petrography 

 of the Millstone Grit Series of Yorkshire ' when it was presented as a thesis 

 for the D.Sc. degree at Leeds University. I was impressed with the ex- 

 haustive character of the research and the thoroughness of the Author's 

 detailed methods. His investigations throw much light on the petrographical 

 characters of these coarse sediments and the probable region from which the 

 main constituents were derived. I agree generally with his conclusions. He 

 has established, in my opinion, that a great part of the constituents of the 

 Yorkshire Millstone Grit closely resemble those found in the Torridonian 

 arkoses of the North-West Highlands. It seems a reasonable conclusion 

 that the materials in this deltaic deposit in Yorkshire were borne by a great 

 river, from a continental land-area in the North where granitic rocks were 

 exposed to denudation similar to those that supplied the abundant microcline 

 in the Torridon Sandstone. The abundance of optically- strained quartz- 

 grains, the micas, the pebbles of chloritoid rock and rhomb -porphj'ry suggest 

 that the river flowed over, or received tributaries from, a region which is now 

 Scotland on the one side and Scandinavia on the other. This conjecture is 

 greatly strengthened by the study of the heavy-residue minerals, especially of 

 the rare monazite, which the researches of Dr. Mackie of Elgin have proved 

 to be comparatively common in the schists and pre-Carboniferous granites of 

 Scotland.' 



Dr. H. Lai'woktii asked whether the Author's researches had 

 enabled him to distinguish the various grit horizons that made up 

 the series. In North Derbyshire the speaker found little difficulty 

 in recognizing and separating the lower grits one from the other 

 in the Held; but in Yorkshire and other areas the individual beds 

 appeared to have no marked characteristics. 



Dr. H. H. Thomas said that he was deeply interested in the 

 work that the Author had carried out. He was especially impr 

 with the extreme abundance, relatively speaking, of certain of the 

 heavy detrital minerals described, more especially of monazite ; 

 for, although the speaker had proved that it was of fairly general 

 occurrence, having found it in the alluvium of the Trent, in the 

 blown-sands of the Hampshire Coast, and the Irish-Sea Drift of 

 Wales, the amount obtained was always inconsiderable. The 

 speaker congratulated the Author, and expressed the opinion that 

 the communication which had just been made to the Society 

 constituted the most complete account of the petrography of a 



sedimentary series that had ever yet been published. 



Mr. W. H. \Vn.< OCKSOS asked whether the Author had detected 

 any trace of pyrrhotite in the Millstone Grit. In work on the 

 sand-tones in the Denbighshire Grit Series of North Wales, the 

 speaker had found this mineral in fair quantity in several of 

 the coarser grits, such as the Corwen and Pen-y-Celog-Grits, and 

 that not only in the unwoatheivd parts, but in the bleached 

 Rurface-layers. In the Welsh grits these layers contained specks of 

 iron-oxide, which seemed to have resulted from the decomposition 

 of some of the sulphide mineral, and similar specks of iron-oxide 



Q.J.G.S. No. 300 z 



