658 PROF, W. BOYD DAWKINS ON THE CARBONIFEROUS, [ Novy. 1902, 
towards the surface in consequence of their northerly dip, letting 
down the surface to a depth of 65 feet below the normal level of 
the rocky plateau. In the district of Northwich the upper thick 
bed of rock-salt, some 80 feet thick, has been carried away by 
natural solution letting down the pre-Glacial land-surface, and 
giving room for very thick and abnormal accumulations of Glacial 
Drift. Many other cases of the same kind have come before me 
in Cheshire, in the course of various enquiries as to the structure 
of the Cheshire saltfield. It may be inferred, therefore, that the 
total thickness of pure salt proved in the two borings is not less 
than 109 feet 8 inches. 
TX. GenerAt Concrvsions. 
When these borings are drawn on the 6-inch scale, and con- 
nected together, as in the originals of figs. 1 & 2, they give a clear 
idea of the sequence of the beds, and of the thickness of the Triassic 
sandstone. It will be observed that the last-named thickens in a 
northerly direction. I have already mentioned the presence of a 
fault in the Yoredale rocks at Ballawhane. A little to the south- 
west of this there is, in my opinion, another fault, letting down the 
Triassic sandstones into the Yoredale Series. In no other way am 
I able to account for the contrast between the sections 1 & 2 at 
Lhen Moar and Ballawhane. 
These borings do not afford sufficient evidence for the construction 
of an accurate map of the solid geology under the Drift. Both my 
map, published in the Transactions of the Manchester Geological 
Society, in 1894, and the map of the Geological Survey, are mere 
sketches, to be modified by the result of subsequent observation. 
The accompanying map (fig. 1, p. 656) has been made by the light of 
the boring at Ballaghenney, which limits the area of the saliferous 
marls, and considerably enlarges the area of the Triassic sandstones, 
as shown 1n my previous map. ‘The Yoredale rocks are also repre- 
sented, as forming part of the waterworn surface underneath the 
Drift. A further addition is that of the Basement Carboniferous 
Beds of the south of the island, which form a thin band at the base 
of the Carboniferous Limestone, instead of occupying the wide area 
shown in the Geological Survey-map. The position of this is, of 
course, hypothetical, and it may, or may not, extend as far south as 
the point where the rocks of the massif rise abruptly above the 
plain between Ramsey and Kirk Michael. The Permians are 
probably faulted down, and covered by the Triassic sandstone, as 
shown in figs. 1 & 2. They may, however, appear on the eastern 
side, as shown in the Geological Survey-map. 
The increase in the thickness of the formations penetrated in the 
boreholes is eloquent of the direction of the dip of the strata. 
