the Displacement of Shore-lines. 503 



depression have been again uplifted, and the raised coral-banks 

 have probablj again begun to sink (at Bombay there is a sunken 

 forest), but the depression has not yet brought them down 

 beneath the sea. 



We may make one or two farther observations upon the 

 Glacial period and its formations. Contemporaneous with 

 "the forest-bed of Cromer" (according to Heer) are the 

 lignites of Diirnten in Switzerland. The fossils show this. 

 They have nearly the same plant-remains, and the same 

 extinct animals. The lignites rest upon and are covered by 

 bottom-moraines, and are therefore " interglacial." They 

 have 7 alternations of peat and forest-beds, and may be 

 fitted into the curve between the arcs 15' and \". From this 

 the Alps must have had large glaciers even during the time 

 of the Red Crag. And there is no improbability in this if 

 we remember that Leda arctica and other Arctic animals were 

 already living on the English coast at this period, and that the 

 Chillesford beds indicate a much colder climate than the 

 subsequent forest-bed of Cromer. 



It is instructive to see how each rising of the sea in England 

 during the Quaternary period had as its consequence the 

 increase of the inland ice. This seems to agree with CroU's 

 theory, that glacial periods are a consequence of great eccen- 

 tricities. But the scanty traces of glacial periods in the older 

 formations, and above all the distribution of glaciers at the 

 present day, show that geographical conditions have the 

 greatest influence. It is only when these are favourable that 

 a high eccentricity can cause the glaciers to increase ; if they 

 are very favourable, there may be a glacial period even during 

 a small eccentricity, as in Greenland at the present day. 

 When the eccentricity increases, the precipitation during 

 rainy periods also increases. If the sea is cold, the precipi- 

 tation will fall as snow, and in this way the glaciers will grow 

 as the eccentricity increases. 



North Germany (according to Jentzsch) has also had three 

 glacial periods with corresponding bottom-moraines (and 

 oscillations?); and in the Alps there have been (according to 

 Penck, Vergletsch. d. deutsch. Alperi) at least three glacial 

 periods. 



We have thus filled up the curve to the present time, and 

 connected the profile of the Paris-basin therewith. We will 

 now trace the oscillations back to the close of the Cretaceous 

 period in order, if possible, to see how many oscillations are 

 included in the Geological period known as the Tertiary. 



The Cretaceous period is separated from the Tertiary by a 

 period of denudation, during which the land was high rela- 



