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succession of continuous undulations, may be almost wholly 
ascribed to the defacing influence of water currents, propor- 
tioned to the local Magnitude of the effects ; and an inquiry 
into the existing drainage, together with the nature and posi- 
tion of the deposits, would seem to confirm this opinion. 
The ranges of hills are composed of arenaceous sandstones, 
sometimes surmounted by millstone, which would resist these 
forces ; whilst the lines along the course of the valleys con- 
sist of the looser shales and argillaceous plate, formations 
readily worn through and acted upon by them. 
As all our valleys situated to the North of the Calder take 
a direction nearly North and South, and the dip of the 
strata at this side Hebden Bridge is almost uniformly to the 
East, powerful diluvial action must have ploughed up the 
strata with a lateral excavating force in their formation, 
sweeping away the spoils over all opposing barriers. From 
what now occasionally occurs in mountainous districts even 
from torrents of rain and swollen springs, we may form a 
faint idea of the devastating effect of the passage of tumul- 
tuous waters when the levels of the country were differently 
adjusted; and the beds of gravel, the masses of granite lodged 
in sand at Mytholmroyd, and the bouldered stones still found 
along the track of the Calder, would indicate that these 
floods had taken that direction. 
Here and there, at several parts of the country, the con- 
struction of the railways has rendered good service to Geology. 
At Millwood, Mr. Gibson, of Hebden Bridge, has been 
enabled by this means to make some important additions to 
his fossil cabinet ; and the specimens of granite, gray wacke, 
quartz, and scar limestone, just alluded to, were lately found 
in diverting the channel of the river at Mytholmroyd. 
To the powerful agencies of seas and fresh water, by far 
the greater part of the phenomena presented to the observa- 
tion of the geologist in the earth's crust are properly referred. 
