INTRODUCTION. 



marshy or partially submerged tracts of level alluvial land. 



We have, however, distinct evidence of old land-surfaces, both 

 in the Coal-measures and in 

 other cases (as, for instance, 

 in the well-known "dirt-bed" 

 of the Purbeck series). When, 

 for example, we find the erect 

 stumps of trees standing at 

 right angles to the surround- 

 ing strata, we know that the 

 surface through which these 

 send their roots was at one 

 time the surface of the dry 

 land, or, in other words, was 

 an ancient soil (fig. 5). 



CONCLUSIONS AS TO CLI- 

 MATE. In many cases fossils 

 enable us to come to impor- 

 tant conclusions as to the 

 climate of the period in which 

 they lived, but only a few in- 

 stances of this can be here 

 adduced. As fossils in the 

 majority of instances are the 



Fijj. 5. Erect Tree conta 

 remains. Coal-measures, No 

 Dawson). 



ng Reptilian 

 Scotia (after 



remains of marine animals, it 

 is mostly the temperature of 

 the sea which can alone be determined in this way ; and it is 

 important to remember that, owing to the existence of heated 

 currents, the marine climate of a given area does not neces- 

 sarily imply a correspondingly warm climate in the neighbour- 

 ing land. Land-climates can only be determined by the 

 remains of land-animals or land-plants, and these are com- 

 paratively rare as fossils. It is also important to remember 

 that all conclusions on this head are really based upon the 

 present distribution of animal and vegetable life on the globe, 

 and are therefore liable to be vitiated by the following 

 considerations : 



a. Most fossils are extinct, and it 'is not certain that the 

 habits and requirements of any extinct animal were exactly 

 similar to, or even at all resembling, those of its nearest living 

 relative. 



b. When we get very far back in time, we meet with groups 

 of organisms so unlike anything we know at the present day as 

 to render all conjectures as to climate founded upon their sup- 

 posed habits more or less uncertain and unsafe. 



