Vol. 67.] ANNIVERSARY ADDRESS OF THE PRESIDENT. 1XXXV 



occur in our area. These sandstones, shales, ganisters, fire-clays, 

 bituminous shales, coals, cannels, and ironstones occur in Britain 

 on two main levels iu the Carboniferous rocks ; but they are never 

 repeated again on anything like the same scale in our British 

 formations. The nearest approach to them is to be found in the 

 Lower Oolites of Yorkshire ; but there is, as it were, some slight 

 attempt at recurrence also in the Tertiary rocks. More than this, 

 it is a remarkable circumstance that more than half of the coals 

 of the Northern Hemisphere are of Carboniferous age. 



Croll, in associating the Glacial Epoch with astronomical causes 

 and their influence on atmospheric circulation, has claimed that 

 the physical configuration of the Atlantic Ocean may have had a 

 secondary influence, in that by its peculiar outline it permitted of 

 important variations in the oceanic circulation of the North 

 Atlantic. Mr. A. R. Wallace has further pointed out that, coin- 

 ciding with these conditions, there possibly occurred an elevation of 

 North- Western Europe which may have allowed the land there to 

 take advantage of the anomalous conditions of solar distance, axial 

 direction, and oceanic circulation, to favour the accumulation of 

 snow on the flanks of the North Atlantic Ocean. According to this 

 suggested modification of the theory, the combination of several 

 causes was required to bring about the remarkable phenomena of 

 that most eventful epoch in our geological history. 



It appears to me that a not less remarkable concatenation of 

 events may have been required to. produce a Carboniferous Period of 

 the extent, duration, and importance of ours ; a Period to which this 

 country owes so much of its commercial and political pre-eminence. 

 In the first place, there was required a wide area of sea graduallv 

 filling up with an unfailing supply of sediment brought by rivers of 

 depth and power. It was further requisite that the sediments 

 should be deposited with great regularity over the large area of a 

 delta in wide flat sheets which seem, as though through isostatic 

 conditions, to have been built up to the level of the sea, not once or 

 twice but frequently, throughout fully the half of a great Geological 

 Period. The deposition must have been accompanied by subsidence 

 not regular but intermittent, with rest-intervals of sufficient length 

 to allow of the growth of swamp vegetation for the varying but 

 lengthy periods necessary for the accumulation of material sufficient 

 to make seams of coal ranging from 2 to 30 feet in thickness. The 

 vast area covered by some of these coal-seams has been compared 

 with that of the forests on some of our modern tropical or sub- 

 tropical swamps and deltas ; but it must be confessed that no exact 



