51 



that any true birds had as yet appeared. Even fish, in the forms 

 most famihar us, had yet to appear ; and the same may be said of 

 several other groups of animals that are better known to the 

 palseontologist than to the general observer. The traces of plants 

 we meet with, bear, like the animal remains, some kind of relation- 

 ship to them that lived in the Carboniferous period ; yet in hardly 

 any case does the resemblance amount to absolute identity. What 

 difference there is seems to suggest that the descendants of the 

 Carboniferous Flora had lived on at no great distance, gradually 

 changing in form as time went on, and now and then extending 

 their area in this direction until changed physical conditions ushered 

 in the newer flora that had long been gradually encroaching upon 

 the ground of the old. Unfortunately, the Penrith Sandstone is 

 singularly destitute of organic remains — Red Rocks nearly always 

 are. It is conceivable that no life could well thrive in water that 

 may be compared to that of a chalybeate spring ; but this hardly 

 accounts for the very remarkable absence of any trace of drifted 

 vegetation.* Can it be that the shore line of the old lake and of its 

 tributaries as well were utterly destitute of vegetable growth ? Did 

 the old lake form a sort of Dead Sea ? It looks very much like it. 

 We know that life was ready to occupy the ground, because as 

 soon as a slight change of physical conditions brought in the rocks 

 that lie on the top of the Penrith Sandstone, that is to say, the 

 Helton Plant Beds, vegetable life seems to have existed in sufficient 

 abundance to form thin seams of lignite and of coal. 



* The deposit of Lignite near the Giant's Caves on the Eamont is a remark 

 able exception. 



