114 PROCEEDINGS OF THE 



shell bed with boulder clay debris. The consistency of the beds 

 composing the series in any section is so different — the boulder 

 clay, the fine laminated clay, the shell bed — are so unequal in 

 resisting power to any pressure, that the immense strain of a 

 sudden upheaval must have confused and contorted them in their 

 relationship to each other. Passing from the physical argument, 

 we find slow stejDS of upheaval distinctly traceable in the existence 

 of littoral and comparatively deep water beds of shells, both in 

 the glacial and more modern deposits. The older clays at various 

 localities present fauna belonging to various depths. We have 

 abundantly, for example, Mija trwicata, and, in equal abundance, 

 Leda pernula. It is the same with many other forms. They 

 represent various depths. While the upheaval of the land was 

 gradual, there are some slight signs that it was possibly undula- 

 tory rather than persistent. This remai"k is not made positively, 

 but as a hint for further observation. He had been surprised to 

 find a Mytilus edulis bed, at the base of a shell bed, rich with 

 Trophon dathratus, Natica clausa, and allied fonns. In one or two 

 cases, where this has been the case, it may have resulted from 

 some accidental accumulation through currents and tides; but it 

 is a point worth watching, as sections are opened at the different 

 clay pits of one locality. The uplifting force Avas not exerted with 

 a uniform power over even limited areas. Take the various 

 heights, from Bute to Airdrie, at which glacial shells are found, 

 and the uplifting force will be seen to have been exerted very 

 variably. There is a littoral shell bed in the clay near the 

 summit of Jordan Hill, 145 feet. The clay bed at Chapelhall, 

 with Tellina jjroxima, is 520 feet above the sea, while the same 

 shell bed occurs at Paisley, Kilchattan, and in the half-tide clays 

 all along our coast. Now, the distance between Jordan Hill and 

 Paisley, in direct line, is very slight, yet there is a difference of 

 145 feet of level in the height of the same littoral shell bed. The 

 upheaval of the land being accompanied with a gradual amelio- 

 ration of climate, this amelioration was subjected to those self- 

 same seasonal variations which occur at the present day. These 

 were oscillations of waiTnth and cold. One curious suspicion may 

 be mentioned as a hint for further inquiry. Mr Jeffrey mentions 

 that at an extensive deposit near Uddevalla, the upper bed gives 

 a similar result. Mixed with the universal Trophon dathratus are 

 many shells of rather a southern type, such as Ostrea edulis, Tapes 



