436 D. MACKINTOSH ON THE ERRATIC BLOCKS OF 
pit near the railway station it is found, as usual, above the middle 
sand. It contains Bunter pebbles, felstone, &c. The large boulders 
disclosed by the plough, pick, and spade in the neighbourhood would 
appear to belong to the base of the sand, the Lower Boulder-clay 
having thinned out. In Market Drayton I saw a number of very 
large boulders of Criffel granite, their surfaces, as usual, rough, 
subangular, or angular. ‘They had been brought from the imme- 
diate neighbourhood, or found in digging for house-sites, &c. I 
could see very little Criffel granite further east than Market Drayton, 
though between that place and Whitmore railway-station, by way of 
Ashley, it was not altogether absent. Between Market Drayton 
and the neighbourhood of Albrighton, Criffel-granite boulders occur 
at intervals; but scarcely any are to be seen between Crudgington 
railway-station and Shrewsbury, and very few west of a line drawn 
from Crudgington to Chester. 
8. Enormous terminal Concentration of Criffel Boulders W.S.W. 
and North of Wolverhampton—Meeting of a cold with a warm 
Current?—Floating ice versus Land-ice-—These granite boulders 
have often been noticed, but no one attempted to work out their 
derivation until 1874, when, from a previous familiarity with 
Criffel granite further north, I had no difficulty in identifying them. 
They are associated with, or rather overlap, a few large and small 
Lake-district felstones and porphyries, a very few Eskdale granites 
and syenites, and a considerable number of Eskdale-granite pebbles*. 
The non-granitic boulders, which were probably transported along 
with them, consist of a kind of ‘‘ greenstone” (lighter-coloured and 
coarser-grained than that found in Cheshire), Silurian grit, sand- 
stone, slate, and metamorphic rocks. JI had seen only one boulder 
resembling Arenig felstone until very lately, when I stumbled on 
one 10 feet in length and almost perfectly angular. It had been 
found on the surface of a deposit of clay, afterwards excavated for 
bricks, near the Wolverhampton cemetery. On sending a speci- 
men of it to Mr. Horne, F.G.S. (of the Geological Survey of Scotland), 
he confirmed my opinion that it did not come from the south of 
Scotland; and on afterwards comparing specimens from it with 
Arenig specimens, I came to the conclusion that it was a miscarried 
boulder belonging to the Arenig overshot load which was precipitated 
around the Clent and Lickey hills. Its position on the surface of 
the clay may have been owing to its having fallen at a later period 
than the Criffel concentration. In the clay-pit I saw a ‘“ greenstone” 
similar to one of the Criffel varieties, a rounded Lake-district fel- 
stone, &c. The great majority of the Criffel-granite boulders le 
between 300 and 600 feet above the sea; but they mostly occur in 
positions, including the lee sides of eminences, which show that the 
* These pebbles have been seattered some distance beyond the boundary of 
the Criffel boulders south of Bridgenorth,:south-east of Bushbury, &e., a fact 
which can be best explained by supposing’ that: the Hskdale granite with the 
Lake-district felstone had been transported before the Criffel boulders. 
+ It had previously been seen and made the subject of an open-air lecture by 
the Rey. H. W. Crosskey and friends. 
