part 4] PETROGRAPHY OF YORKSHIRE MILLSTONE OBIT. 281 



that the only possible area lay still farther north, in what is now 

 the Xorth of Scotland, and its extension lay east with a larger 

 Scandinavia, thus forming part of a great continental land, the 

 limits i northern and western) of which it is not at present 

 possible to define. This is a conclusion to which previous workers 

 in the same field have arrived, namely, Sorby, 1 and Hull, 2 while 

 their views have been endorsed by Green. 3 The last-named quotes 

 Sorby on this subject, and, in the map which he gives of Lower 

 Carboniferous geography, we find that he has represented the 

 boundary of the extension of this Scoto-Scandinavian land as lying 

 quite close to the present eastern coastline of the Northern 

 counties of England, crossing it at Spurn Point into Lincoln- 

 shire, and joining up with the Central Ridge before mentioned. 

 An isthmus of the Southern Uplands connects it with a large 

 land-mass which sends off a tongue to embrace the north of the 

 Isle of Man and the Lake District, while another large lobe to 

 the west takes in the North- West of Ireland. The Central Valley 

 of Scotland forms an inlet open to the ocean in the west. 



A. J. Jukes-Browne 4 criticizes this map, and proposes to join 

 up the Xorth of Ireland with Scotland north of the Central 

 Valley, and to open a way between the South of Ireland and 

 the South of England. In his own map 5 he has made these 

 alterations, and introduces changes in the boundaries of the 

 Central Ridge, which he connects up with Ireland and the South- 

 West of Scotland. It is not my intention to discuss the boundaries 

 of the Lower Carboniferous Sea : I have merely given these refer- 

 ences and descriptions, in order to make it clear that all workers 

 in this subject agree that the great northern land-mass did exist, 

 and that Scotland and Scandinavia were undoubtedly connected in 

 Carboniferous times. 



Only Sorby, however, had adduced any evidence from the litho- 

 logical side, and all subsequent writers to the present time have 

 been content to quote his work, the reliability of which has never 

 been questioned, and the result of the work herein described is to 

 confirm the view put forward by Sorby some sixty years ago. 

 This northern land satisfies the conditions required as to type of 

 rock: though many of the pebbles which are here figured and 

 described cannot be definitely traced, yet one cannot fail to be 

 impressed with the resemblance when the whole facies is taken 

 into account. (See map, fig. 2, p. 280.) 



X. Physical Relief of the Ancient Land-Mass. 



The Carboniferous Limestone was certainly not deposited in a 

 sea of great depth ; on the contrary, it exhibits throughout its 



1 Proc. Yorks. Geol. & Polytechn. Soc. vol. iii (1859) p. 675. 

 - ' Physical History of the British Isles ' 1882, p. 37 ; and Trans. Roy. 

 Dublin Soc. ser. 2, vol. iii (1885) p. 305. 

 8 ' Coal : its History & Uses ' 1878, p. 38. 



4 • Building of the British Isles ' 2nd ed. (1892) p. 131. 



5 Ibid. p. 123. 



