NOTES ON THE GEOLOGY OF 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 Whitby. 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 inchne-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 sihca, 
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 Avhich 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 Fell, in Durham, to Maybecks, in the east of the North Riding — 
a distance of seventy miles. It is unaccompanied by any dislocation, 
