IV] OLD SURFACE-SOILS. 57 



trees which grew in the Portland forest. The beds separating 

 the surface-soils of the Purbeck Series, as seen in the sections 

 exposed on the cliffs or quarries, point to the subsidence of a 

 forest-covered area over which beds of water-borne sediment 

 were gradually deposited, until in time the area became dry 

 land and was again taken possession of by a subtropical vegeta- 

 tion, to be once more depressed and sealed up under layers of 

 sediments 



A still more striking example of the preservation of forest 

 trees rooted in an old surface-soil is afforded by the so-called 

 fossil-grove in Victoria Park, Glasgow, (Frontispiece). The 

 stumps of several trees, varying in diameter from about one to 

 three feet, are fixed by long forking ' roots ' in a bed of shale. 

 In some cases the spreading ' roots,' which bear the surface 

 features of Stigmaria, extend for a distance of more than ten 

 feet from the base of the trunk. The stem surface is marked 

 by irregular wrinklings which suggest a fissured bark ; but the 

 superficial characters are very imperfectly preserved. In one 

 place a flattened Lepidodendron stem, about 30 feet long, lies 

 prone on the shale. Each of the rooted stumps is oval or 

 elliptical in section, and the long axes of the several stems are 

 approximately parallel, pointing to some cause operating in a 

 definite direction which gave to the stems their present form. 

 Near one of the trees, and at a somewhat higher level than its 

 base, the surface of the rock is clearly ripple-marked, and takes 

 us back to the time when the sinking forest trees were washed 

 by waves which left an impress in the soft mud laid down over 

 the submerged area. The stumps appear to be those of Lepi- 

 dodendron trees, rooted in Lower Carboniferous rocks. From 

 their manner of occurrence it would seem that we have in 

 them a corner of a Palaeozoic forest in which Lepidodendra 

 played a conspicuous part. The shales and sandstones con- 

 taining the fossil trees were originally overlain by a bed of 

 igneous rock which had been forced up as a sheet of lava into 

 the hardened sands and claysl 



Other examples of old surface-soils occur in different parts 

 of the world and in rocks of various ages. As an instance of a 



1 Buckland (37) PL lvii. » Young, Glen, and Kidston (8H). 



