NOTES ON THE GEOLOGY OP CLEVELAND. 



93 



now worked, are entirely without other foundation than the above 

 instinctive notion. 



I had almost forgotten to mention another seam of iron-stone 

 amongst these higher strata, which has a more argillaceous aspect 

 than the others, though its thickness is less considerable. It is, as 

 all the other strata, of anything but uniform thickness; and at present 

 the only place where it has been fully explored and worked to any 

 extent is at Burton Head, near Ingleby Greenhow. It has, I believe, 

 also been worked at Raithwaite, near WTiitby. At Ingleby mines 

 the stone was found to obtain in three bands, with shale intervening, 

 giving a total of rather more than four feet of iron-stone, and two and 

 a half of shale between. These mines, however, are for the present 

 abandoned, although a great sum has been laid out on an incline-plane, 

 and other preliminaries to active operations. 



To anyone who is familiar with the section of the Bath Oolite, in 

 the south of England, it must be at once apparent how different are 

 the analogous beds, in the district which I have been describing. 

 This last great division (/), is isochthonous with the Fuller's-earth 

 group of Bath, although we can see so, little similarity in their com- 

 ponents. 



g, The last division in my section is the earliest wherein is any 

 trace of a limestone rock ; and its aspect in Commondale, where we 

 see it most easily, bears little or no resemblance to the type of an 

 oolitic limestone. It is very much debased by an admixture of silica, 

 iron, and other extraneous matter, which causes it to be of little value 

 for agricultural purposes. So little indeed is it regarded as a lime- 

 stone, that it has long since ceased to be burnt for any purpose ; and 

 whilst it was regularly burnt formerly at the kilns on the high moor- 

 land above Commondale, great care had to be taken lest it should run 

 into a flux from too intense a heat. Although as a limestone its value 

 can never be considerable, yet if silica were required with any argil- 

 laceous ironstone to help to form a clay, it might probably be of service 

 to any furnace near where it exists : as such however is very impro- 

 bable with most of the Cleveland iron-seams, we can only wish it had 

 been more calcareous. I append an analysis of this seam as at 

 Commondale, made by Prof. Henry, who gives a much more favour- 

 able one than appears in Prof. Phillips' " Geology of Yorkshire." 



Above this limestone is another very thick series of sandstones, 

 shales, &c, very similar to those in group /, of which I have often 

 spoken. As they present little that is noticeable, I shall not attempt 

 to examine them, although we find them occupying some of the 

 highest ground in North Yorkshire, as at Danby Beacon and White 

 Cross. With this notice I shall conclude my observations on the 

 sedimentary rocks, and proceed to make a few remarks upon the only 

 igneous rock which we find in the district — the well-known basaltic 

 dyke, which has been termed " one of the most remarkable phenomena 

 of English geology." It extends in almost a straight line from Cock- 

 field Pell, in Durham, to Maybecks, in the east of the North Riding — ■ 

 a distance of seventy miles. It is unaccompanied by any dislocation, 



