A HISTORY OF CUMBERLAND 
expressed by speaking of these productive beds as ‘ Coal Measures,’ with 
some qualification connected with the locality where they occur. Thus 
we may speak of the Whitehaven Coal Measures, even though the beds 
in question may prove to be (as the present writer has long believed) of 
the same age as the Upper Yoredales and the Millstone Grit. In like 
manner we may speak of the Brampton Coal Measures, or the Newcastle 
Coal Measures, even though it may prove, as just stated, that no rem- 
nants of the true Coal Measures occur anywhere in Britain to the north 
of the tiny remnant before referred to as occurring in the basin of the 
Eden. 
(e) Organic Remains from Carboniferous Rocks.—Just as the animals 
and plants of the Devonian Period mark a stage of organic evolution 
greatly in advance of that presented by Silurian life, so does the life of 
the Carboniferous Period, on the whole, surpass the Devonian. Probably 
the waters of the Carboniferous seas in the Cumberland area had a 
moderately high maximum temperature, and a minimum temperature 
but little below the mean. These are amongst the conditions most 
favourable for the development of animal life in the sea ; and they are 
almost equally favourable for the growth of vegetation on the land. The 
chief organic advance was made by the Vertebrata, as some of the higher 
grades of fishes (probably the Dipnoi, the ancient representatives of the 
modern Ceratodus) gradually took to an amphibious mode of life, which 
in time led to the evolution of the Amphibia, from which parent stock 
first the Anomodontia, and then the true Reptiles and the Birds, as well 
as the Mammalia, eventually arose. 
It is very interesting to note that several air-breathing Invertebrates, 
of forms not very distantly removed from those now living, had already 
come into existence in Carboniferous times. The Scorpions and the 
Galley Worms are especially noteworthy in this respect. 
As for the vegetation, we have abundant evidence of what that was 
like, even though the remains are those of plants grown at a distance. 
No plants of grade quite as high as the true Conifers had yet arisen. 
The bulk of the forest growth consisted of gigantic plants of much lower 
grade than the firs, a large number of which were allied to the Club 
Mosses (especially to Se/aginella). With these were others, distantly 
allied to the modern Equisetums. It is from the spores, and from the 
macerated leaves and vegetable tissues of these in general, that our coal 
seams have arisen. 
(7) A computation of the time required for the formation of the 
Lower Carboniferous Rocks, estimated chiefly on the assumed rate of 
one foot in 25,000 years for the marine limestones, gives 62,000,000 
years. To this has to be added the time required for the formation of 
the coal seams and the other rocks of Upper Carboniferous age, occur- 
ring in other parts of Britain, which is here set at 31,800,000 years. 
This gives a total of 93,800,000 years as the time required for the 
formation of the whole of the Carboniferous Rocks. 
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