Vol. 50.] BAILWAT FROM EOMEOED XO TTPMINSTEE. 451 



clay containing ' race ' resemble in their nature and arrangement the 

 beds beneath the Upper Boulder Clay of Hendon and Finehley. 

 But they seem to me to suggest with equal force the gravel, sand, 

 and clay or loam which are the usual constituents of river-drifts, 

 and the order in which these usually occur. ' Race,' again, may 

 be found in clays and loams of the most diverse ages. In the 

 chapters on the Woolwich and Beading Beds in Mr. Whitaker's 

 memoir on the Geology of London ' race ' is said to appear in clay 

 or. loam in at least ten different sections. It is also given as a con- 

 stituent of the river-drift of the Thames Valley at Ilford, Erith, 

 and Crayford. Thus its presence has no particular significance, and 

 affords no presumption as to age. 



Then there is the thin stratum of dark loam in which the mammoth- 

 remains were found, and which appeared to pass insensibly into 

 the London Clay on which it rested. This seems to me to be partly 

 mud deposited in the channel of the river where the current was 

 particularly sluggish, and partly material resulting from the contact 

 of the river-water with the London Clay. Of course, a river is 

 always tending to shift its course laterally. Thus a part of its 

 channel where the current was once extremely sluggish gradually 

 becomes the scene of more rapid motion, and gravel is deposited 

 where once only mud in suspension slowly descended to the bottom. 

 Prom the fact that gravel is usually the lowest of river-deposits we 

 learn that any mud settling down where the current is sluggish is 

 generally swept away when the current becomes swifter, and gravel 

 is being deposited there. But here and there, in hollows, a little 

 mud would be preserved, and the carcass of a mammoth, for instance, 

 sinking into mud at the bottom of a river-channel would form an 

 obstruction, resulting both in the deposition of an unusual thickness 

 of mud and in the preservation of the animal's remains. 



Again, the yellowish clay forming the surface-bed at and near 

 Endsleigh Street, below the ' made ground,' seems to me to be the 

 equivalent of the brick- earth of Ilford and other places in the 

 Thames Valley which has yielded so many mammalian and other 

 remains. I am aware that some geologists have shown an inclina- 

 tion to separate the brick-earths of the Thames Valley from the 

 sands and gravels associated with them, on account of the fossil 

 contents of the former beds. But it never appeared to me that 

 there are any good grounds for such a proceeding. For they were 

 all alike river-deposits formed contemporaneously, the gravel and 

 sand having been brought down the river-channel, while the over- 

 lying brick- earth or clay was simply the inundation-mud which had 

 spread over the adjacent flats in times of flood. And it seems 

 obvious that an elephant or other large mammal, which had become 

 drowned during a flood, would often be stranded on the alluvial 

 flat, and his bones remain preserved by later deposits of mud, 

 showing to observers of the present day every sign of tranquil 

 deposition. On the other hand, creatures which continued to float 

 down the river were extremely unlikely to have their remains pre- 

 served at all. 



