254 EECENT FORMATIONS. 



through their subsoils to be convinced of the truth of this 

 origin. A thick layer of vegetable or peaty soil, followed 

 by beds of silty sand, marl, and clay, imbedding the bones 

 of deer, oxen, and other animals, with the remains of an 

 occasional tree-canoe, clearly bespeak their lacustrine forma- 

 tion, and point to the time when the wild animals of the 

 country were mired in their muds, and the primitive inhabit- 

 ants paddled across their waters. JSTow how changed ! the 

 site of the former lake green with the richest pastures, or 

 waving with luxuriant corn-fields ! As with the straths and 

 dales of Britain, so with a large proportion of all the inland 

 plains and valleys of the world. Many of them are but 

 chains of silted-up lakes converted into dry land, partly by 

 the process of silting or filling up, and partly by the main 

 stream of the valley cutting deeper and deeper its channel, 

 and thus affording a more thorough drainage for the whole. 

 Lacustrine formations, though occurring in the same plain 

 with those of fluviatile origin, are in general readily dis- 

 tinguishable by their finer sediments, greater regularity of 

 deposition, the occurrence of beds of shell-marl and peat, 

 and the more perfect preservation of their organic remains. 

 These remains are often of great antiquity, ranging from 

 the time of the mammoth, great Irish deer, and species of 

 oxen that have been long extinct, down to the pile-dwellings 

 of our Celtic or pre-Celtic ancestors, who betook themselves 

 for safety to their waters, and erected artificial mounds for 

 their habitations, where nature had not provided the neces- 

 sary "inches" or islands.* Even since the time ^of the 



* Since 1854 these lake-dwellings or pile-dwellings (known as pfahl- 

 ^iten in Switzerland, and crannoges in Ireland), have received much 

 attention from archaeologists and geologists. These dwellings occur in 

 existing lakes, as well as in bogs and marshes which were formerly the 

 sites of lakes, and seem to have been erected on piles driven through 

 the water, or on mounds partly formed of stones, wood, and other 

 debris. They have been found in Switzerland, Ireland, Scotland, and 



