ATKINSON: HIS TOBY AND OBJECTS OF THE SOCIETY. 5D 
was destined to immortalise their names. Then it was that 
geologists were divided into Gatastrophists, or those who 
believed that the history of the earth was that of periods 
of repose alternating with catastrophes and cataclysms of a 
more or less violent character ; and Unifovmatists, or those 
who believed that, in spite of all apparent violations of the 
laws of continuity, the sequence of geological phenomena has 
really been a regular or uninterrupted one. Of the latter 
theory, which is now generally received, Sir Charles Lyell 
was the most distinguished advocate ; of the former, Sir R. 
Murchison. 
With respect to the geology of this district, very little 
need be said about it, as my friend Dr. Parsons has so ably 
treated the subject in his valuable paper, read before the 
Ripon meeting of this Society last year, " On the Strata of 
the lower Ouse Valley;" but the following brief account may 
be interesting. 
Selby stands on the level surface of the great alluvial 
deposits through which the rivers of Yorkshire and Lincoln- 
shire pass to the Humber. In those parts of the district which 
lie within the reach of the tide, the surface soil is composed of 
a soft fertile loam, locally termed " warp/' in places many 
feet thick, and having its source in the sediment held in 
suspension in the river water. Below this, and usually form- 
ing the surface in those parts of the district above the reach 
of the warp, is a bed of loose yellow sand ; and below this,, 
again, is a strong brown laminated clay, in places nearly 
sixty feet in depth, and sometimes presenting thin inter- 
calated beds of sand. Below the laminated clay are gravels, 
sands, and clays, belonging probably to the glacial period. 
At Escrick Station a tough brown clay is to be found, with 
embedded, smoothed, and ice-scratched boulders of car- 
boniferous limestone. 
Beneath all these lie the stratified deposits of red 
