136 ORGANISMS FROM THE RECENTLY-DISCOVERED 



slopes. The continuance of this deposit was certainly prolonged, 

 as the quantity of matter deposited in any single year must be 

 represented, in its now compressed form, by a very thin layer. 

 Eventually these deposits ceased, and then the surface became 

 adapted for the growth of rushes ; in fact it became a morass, and 

 this condition of things prevailed long enough to allow of the 

 deposit of decayed rushes to the depth of two feet. At the close 

 of this period the river bed appears to have been cleared of its 

 obstructions, probably by the hand of man, as the bed overlying 

 the rush deposit is of artificial origin. The works of civilisation 

 were again resumed, and the surface of the river valley underwent 

 a corresponding change. 



" It is difficult, without personal examination, to describe with 

 accuracy the physical changes that took place, and which led to 

 the formation of these deposits ; but in all the river-valleys of this 

 part of the country, where the current is not very rapid, there 

 must occur in the natural condition of things, obstructions of the 

 nature of those I have suggested as having occurred at Bath. In 

 the valley of Frome, near Stroud, there are many flat meadows 

 which owe their origin to similar conditions. The section is inter- 

 esting, inasmuch as it shows that a state of change still exists, that 

 the operations of nature, under which the surface of the high lands 

 is being denuded, are still going on, and where, as in the present 

 instance, some of the results are capable of measurement, they 

 are shown to be neither slight nor unimportant." 



Beyond this opinion a large amount of interest centres in the 

 probability, that at one time the tide flowed up the river as far as 

 the site of the bath.^^ I am gready indebted to Mr. Rimmer, 

 F.L.S., of London, whose recent, admirable book on " The Land 

 and Fresh-Water Shells of the British Isles," enabled me to cor- 

 respond with him. He has not only been kind enough to com- 

 plete the naming of the shells, which I shall presently describe, 

 but he calls attention to one species found, not in the mud 

 bank, but mixed with the sand and soil of the ambulatory in 

 great abundance. This species is known to inhabit only brackish 

 water, and besides these shells, some diatoms which I have found 



* This must have been impossible on account of the great difference in level 

 between Bath and the highest tidal point of the Avon.— Ed. 



