42 REPORT OF MEETINGS FOR 1901 



there is good reason for the belief that both the cold winds 

 of our spring, and the frosts of our winters, were conspicuous 

 by their absence. Furthermore, it seems to be a well-established 

 fact* that the temperature of the surface-water of the sea, 

 upon which the well-being of so many living things depends, 

 was not liable to changes of anything more than small extent. 

 Lastly, it may be stated here that there does not appear to 

 be any good reason for the belief, once widely held, that 

 the atmosphere of Carboniferous times contained any higher 

 percentage of carbonic acid than does that of any part of 

 the globe of to-day. Equability of climate characterised the 

 whole of the immensely-long period during which the Lower 

 Carboniferous rocks of Britain were in process of formation. 



A vast thickness of rocks of various kinds accumulated in 

 the northern parts of the kingdom during the period in 

 question. The thickness of the Lower Carboniferous strata 

 near Edinburgh, for example, amounts to some seven or eight 

 thousand feet. As a large part of these rocks were formed 

 in seas of moderate, or of small, depth, it must be clear that 

 the sea-bottom, throughout the whole of the period while these 

 strata were accumulating, must have been undergoing sub- 

 sidence. There is evidence to show that the subsidence in 

 question was more pronounced in the southern parts of the 

 area, so that the floor of the sea there was occasionally let 

 down by the sinking of the Earth's crust to a very considerable 

 depth below the upper level of the sea. The downward 

 movement was by no means continuous ; as there is clear 

 evidence of long pauses between the subsidences, during which 

 the land remained nearly at the same level. The movements 

 of depression which led to the change from shallow to deep 

 water conditions appear to have been usually somewhat abrupt ; 

 and, furthermore, these abrupt downward movements were, 

 after a long interval of time, usually followed by some move- 

 ment in the opposite direction. The net result of these 

 oscillatory movements was, however, one of subsidence. 



Kivers draining the old continent mentioned above as lying 

 to the north-west of our present land, slowly transferred the 



* Goodchild, Trans. Geol. Soc,, Glasgow, Vol. Xll., pp. 34-38 5 &n^ 

 froc, Boy. Phya. Soc, Vol. xv,, p. 62, 



