1889.] THE DISPLACEMENT OF BEACH-LINES. 37 



Dawson expresses the thought (1. c. p. 176—179) that the 

 remarkable regularity, with wich these cycles return, may per- 

 haps be owing to a cosmic cause, and be dependent on one or 

 other astronomical period. But he appears to reject that idea 

 subsequently, because the Palaeozoic cycles have layers that 

 are 4—5 times as thick as the Mesozoic (1. c. p. 195). We 

 might therefore suppose that a longer time must have been- 

 necessary for their formation. But he accentuates, on the other side, 

 that in the Palaeozoic period the changes in the organic world 

 took place more slowly, in relation to the formation of beds, 

 than subsequently, so that the fossils extend through greater 

 thicknesses than in the less thick later cycles. If I were to 

 draw a conclusion from these facts cited by Dawson, I would 

 arrive at a different result from him. I would consider it rea- 

 sonable to assume that the formation of beds in the Palaeozoic 

 epoch proceeded more rapidly than afterwards. If the Moon was 

 at that time closer to us and the sidereal day shorter, as 

 Dane i,> has supposed, the tidal- wave must have been both stronger, 

 and have acted more frequently than now. The coast would be 

 destroyed far quicker, and the sea would obtain much more stuff 

 to precipitate. A cycle of that time would have a greater thick- 

 ness of layers than a later and younger one, and the fossils 

 would extend through a greater thickness of bed than in the 

 latter. I see, at present, no reasonable ground for supposing 

 that the development of new species would be accelerated in the 

 same degree as the formation of beds. 



There is, therefore, reason for supposing that it is these 

 changes in the Earth's form, occurring at long intervals, that 

 enables us to distinguish between geological formations. But 

 such great changes in the divisions of land and seas must, of 

 necessity, produce also considerable changes of climate, and along 

 with that, surely enough, changes also in the forms of animal 

 and vegetable life. In one of my previous Papers I have already 

 proposed the view that the glacial epoch was caused by a change 

 in the division of land and seas. If the land obtained a great 

 distribution in the middle and higher latitudes, especially if tun- 



