48 POST-TERTIARY ENTOMOSTRACA. 



often insecure, owing to impermeable hollows filled with silt or other porous material, 

 and grown over with turf, which may remain in this state indefinitely, while the 

 surface continues to supply the water, and the basin to retain it. Such conditions 

 are well known to agriculturists, whose skill is exerted in discovering how they can best 

 draw off the imprisoned water which impedes the fertility of their lands over particular 

 areas. 



The Boulder Clay, it may be added, is softer at the bottom of the trough immediately 

 under the laminated clay than at a greater depth, doubtless owing to contact with the 

 moister clay above. 



There are facts, moreover, which cannot be reconciled with any mere drifting 

 agencies. 



1. The large boulders embedded in the shelly deposit. Many of these had marine 

 organisms attached to them, and were not less than half a ton in weight. 



Even with modern appliances one of these large blocks could not (the contractors 

 informed us) be removed without blasting, and not one of them when uncovered had the 

 shghtest mark of a mallet or bore of a blast upon it. 



2. Had the fossiliferous material been dug up from one place and carried to another 

 by human agency, unmistakeable tool-marks, cuts, and indentations of pike and shovel, 

 would have been visible on the shells in their crowded condition ; but not a single mark 

 of this kind has been found. 



3. Although the great mass of the shelly deposit lies in some apparent disorder, the 

 under portions of it are distinctly laminated. Resting on the Boulder Clay there is an 

 unevenly thin bed of reddish-brown clay, made up of very fine layers. Overlying this is 

 a layer of whitish clay, about six inches thick, which is again covered by a layer of light 

 grey clay, about one inch thick. These layers can be traced over the bed and up both 

 sides of the trough, and it is impossible that sediment washed down through the loose 

 materials above, as has been supposed, could have been accumulated in this manner. 

 Again, had the layers been the immediate washings of the upper material, they would 

 have been similar in colour and composition ; but all three differed largely from the 

 overlying clays, as well as amongst themselves in colour, constitution, and fossil 

 contents. 



The thin fight-grey layer lying between the whitish six-inch layer and coarser shell-clay 

 above contains one Polyzoon {Idmonea fenestrata. Busk) far more abundantly than we have 

 found it elsewhere in the section. In this thin layer also occur the asbestos-like fibres of 

 the shell of the common Mussel {Mi/tilus edulis), of which we have not found a vestige in 

 the overlying clays. The six-inch stratum of whitish clay is, when dry, of an extremely 

 friable character, and very like a stratum of clay met with in some of the Paisley brick-fields, 

 and at Jordan Hill, in the same relative position ; and the reddish-brown clay underlying 

 this corresponds with the thinly laminated clays frequently found at the base of the fossili- 

 ferous clays of the Clyde district. Further, these underlying strata all contain organisms 



