of the Valley of the Thames. 167 



sizes, from that of a marble to an orange, and occasionally very 

 much larger, of a light brown colour, soft to the touch, smooth, 

 and either compact or made up of concentric laminae, in outward 

 appearance resembling Websterite, for which I had always taken 

 them until very recently ; but a careful analysis has shown that 

 they are composed almost entirely of carbonate of lime, with a 

 slight addition of phosphate and sulphate of lime, a little phos- 

 phate of alumina, silica, and peroxide of iron ; they are chiefly in 

 the upper layers of clay and not intermixed with the bones. 

 Vegetable remains are scarce, but a large bed of lignite was dis- 

 covered in the brick earth some time back. Dr. Lindley has 

 kindly examined its structure, and reports that all he can assert 

 is, it is not coniferous, that it contains some dotted tissue resem- 

 bling that seen in elm, but presents no character by which its 

 affinity can be determined. 



The circumstances under which the bones are discovered lead 

 to the conclusion that the animals lived and died near the spot 

 which incloses their remains ; the skeletons are frequently entire, 

 and have not suffered by attrition, and the presence of teeth of the 

 young Elephant is opposed to the view that they may have migrated 

 here upon some general geological change and have been subse- 

 quently destroyed. The strata were evidently quietly deposited, 

 the shells are in general well preserved, and the stratification of 

 the sands indicates the long continuance of causes alternating 

 with one another and uninterrupted by violence. The freshwater 

 origin is decided by the characters of the shells, all being of this 

 class with the exception of the Helix, which, like the recent spe- 

 cies with which it is probably identical, may have lived upon the 

 banks of rivers and been buried with its aquatic neighbours. 

 The arrangement of the strata does not differ from that seen in 

 the bed of modern freshwater lakes and rivers, especially in those 

 subject to occasional inundations ; giving great probability to the 

 idea that they were formed during the elevation of older strata, 

 when large quantities of solid materials were washed away from 

 the rising mass, and deposited in hollows and valleys by the 

 agency of water. 



It is not impossible that the thick layers of gravel beneath the 

 brick earth were the result of a breaking-up of a portion of the 

 chalk originally covering the Wealden, and that the clays and 

 sands were supplied by the partial destruction of the Wealden 

 itself; the similarity in the materials of the two formations is 

 very conspicuous, and the frequent occurrence of calcareous 

 masses adds great weight to such an hypothesis, especially as 

 many of the nodules appear to be merely rolled pieces of chalk, 

 with some earthy additions which may have been supplied by the 

 clay in which they are found, and those more distinctly laminated 



