410 W. TOPLEY AND G. A. LEBOTJR ON THE INTRUSIVE 



sented as accepting Sedgwick's conclusions as to the intrusive 

 character of the Whin Sill in Teesdale ; but this must he an 

 error *. 



Professor Phillips, giving most weight to the conformable nature 

 of the beds in Teesdale and along the Penine escarpment, considered 

 the Whin Sill to be of contemporaneous date ; and he accounted for 

 the altered nature of the overlying beds by supposing that the heat 

 from such thick masses of lava had not time to escape before these 

 beds were deposited. He admits some eruptive force, but apparently 

 only so far as to allow of the Whin reaching the sea-bottom, over 

 which he supposes it to have flowed f . 



The late Mr. G. Tate published several papers on the Geology of 

 Northumberland, particularly on the northern part of the county. 

 Frequent mention is made of the Whin Sill, and illustrations of its 

 intrusive character are given. These papers t were published in the 

 Transactions of local societies, or in books relating to Northumber- 

 land. Had they been published in works generally accessible to 

 geologists, the question in dispute would probably have been settled 

 years ago. 



Of other geologists who, from personal knowledge, admit the in- 

 trusive nature of the Whin Sill we may name Mr. Howse, Mr. Kirkby, 

 and the whole of the officers of the Geological Survey to whom the 

 district is known §. 



Amongst those who, in published papers, regard it as interbedded 

 and contemporaneous are Professor H. A. Nicholson, Mr. Bewick, 

 Mr. J. A. Knipe, and Mr. N. Wood ||. 



The intrusive nature of the Whin Sill is shown on the Maps and 

 Sections of the Geological Survey if. In the year 1873 we laid 



* The paper read at Newcastle is published in full, and it received additions 

 and corrections by the author before publication. This, therefore, certainly 

 represents Hutton's views correctly ; and here he dissents entirely from Sedg- 

 wick's conclusions. 



t Geology of Yorkshire, part ii. p. 85, 183b\ At the Bradford meeting of the 

 British Association, when some of the facts hereafter mentioned were laid 

 before the Geological Section, Professor Phillips admitted that we had proved 

 the intrusive nature of the Whin Sill for the districts described. 



j The most important paper is that " On the Basaltic Rocks of Northumber- 

 land," Proc. Berw. Nat. Club, vol. vi. p. 197. See also papers in vol. iii. pp. 99, 

 233 ; Tate's History of Alnwick, vol. ii. p. 461, 18(59 ; and other works. 



§ Mr. W. Boyd (Trans. N. Engl. Inst. Eng. vol. ix. p. 185, 1861) described 

 the Whin Sill of the northern part of Northumberland as contemporaneous. 

 He now believes it to be intrusive; Mr. Hedley is also of this opinion. 



|| In the paper, as laid before the Society, full reference to all publications on 

 the subject were given. In the discussion which followed the reading of this 

 paper, Mr. W. W. Smyth stated that Mr. Blackwell regarded the Whin Sill as 

 intrusive. We have been unable to find any published opinion by him on the 

 subject. 



^f Sheet 105 N.W. was published in 1871 ; this map (by the authors of this 

 paper) includes the Whinstone area near Kirkwhelpington. Several sheets of 

 the six-inch map of Northumberland, including parts of the Whin Sill, are pub- 

 lished. Sheet 108 of the Horizontal Sections, by Mr. H. H. Howell, was pub- 

 lished iu 1875 ; in this the Whin Sill of Great Swinburne is marked as an intru- 

 sive sheet. 



