CHARACTER OF THE WHIN SILL OF NORTHUMBERLAND. 407 



High-Cup Nick, about 4 miles east of Appleby. Here the Whin Sill 

 (75 feet thick), and the beds above and below it, are beautifully 

 exposed. The roof and floor of the basaltic sheet consist of shale, 

 both equally baked and altered for several feet from the line of con- 

 tact with the Whin. 



As regards this escarpment, the continuous interbedding of the 

 Whin has been simply assumed ; the evidence, when carefully 

 examined, tells the other way. Mr. J. G. Goodchild, E.G.S., of the 

 Geological Survey, has proved that the trap is certainly intrusive 

 here. In a letter to *us (dated Jan. 27, 1876) he says that at 

 Kenwick the Whin " is found at from 250 to 300 feet below the 

 Eour-fathom Limestone. In another part it comes immediately 

 below the Scar Limestone ; and as one follows the outcrop [south- 

 wards] towards Brough, it is found at successively lower horizons, 

 until near Roman Pell it lies on the top of the Melmerb}'-Scar Lime- 

 stone. In other words, between Renwick and Brough [19 miles] 

 the Whin Sill cuts through about GOO feet of the Carboniferous 

 Limestone Series." 



Mr. C. T. Clough, of the Geological Survey, has recently shown 

 that even at the typical section of High Force itself the Whin can 

 be shown to be intrusive ; and he adds : — " I have very little doubt 

 that the more the country is worked over, the more and more evident 

 will the intrusive character of the Whin Sill become*. 



It may be well to mention that the term Whin is rather loosely 

 used in the north of England. Basalt is so termed ; but the word is 

 also applied to the Porphyrite of the Cheviots and to any unusually 

 hard quartzose sandstone. The hard sandstone is sometimes spoken 

 of as " white " or " grey " whin, whilst the Basalt is called " blue 

 whin." The hard cherty sandstone which occurs in the Lower Green- 

 sand of West Sussex is called Whinstone ; and the term " whin " is 

 applied to hard sandstone in the South-Wales Coal-field. In 

 Leicestershire it is applied to the remarkable bed of trap which 

 occurs at the south-eastern part of the Coal-field, and also to hard 

 sandstone or chert. 



In the lead-mining districts of the north of England the various 

 beds are called " Sills." As the miners have always regarded the 

 basalt as a true bed, it has been called the " Whin Sill." It is also 

 sometimes called the " Great Whin Sill," to distinguish it from the 

 " Little Whin Sill" of Weardale. We believe both of them to be 

 branches of the same intrusive sheet. 



2. The Carboniferous-Limestone Series of Northumberland. — In 

 order that the following details may be understood, it is desirable to 

 give some account of the succession of beds below the Millstone Grit 

 in Northumberland. It is customary to retain for the north of 

 England the old-established divisions of Coal Measures, Millstone 

 Grit and Carboniferous Limestone. These names were first given in 

 the south-west of England, where well-defined divisions correspond- 

 ing to them exist. But if the Carboniferous Series had been first 



* Quart. Journ. Geol. Sue. vol. xx\ii. p. 171, 1870. 



