HISTORY OF GEOLOGY AND PALAEONTOLOGY. 



Croll and J. H. Schmick. These observers also supposed that 

 periodic attraction of the ocean-water now towards one 

 hemisphere, now towards the other, caused variations of climate 

 and fluctuations of level. But if this hypothesis be correct, 

 there ought to be extensive regions of depression or elevation; 

 local movements in opposite senses, and especially oscillatory 

 movements, are excluded. Dana's assumption of a widely- 

 extended movement of elevation towards the North Pole has 

 been supported by Sir Henry Howorth, whose idea is that the 

 land is rising at both the Poles and contracting at the Equator. 



From the actual distribution of the geological formations, 

 Dr. Trautschold inferred the probable conditions of the earth's 

 surface during past epochs, and argued that the volume of water 

 in the ocean has gradually been diminishing. As immediate 

 causes of diminution, he specified the accumulation of masses 

 of snow and ice on land areas, the formation of inland seas 

 and rivers, the absorption of water in consequence of the 

 hydration of rock-forming minerals, and the consumption of 

 water in the organic world. Dr. Trautschold by no means 

 contested movements of crust-elevation, but thought many 

 cases of so-called secular upheaval explicable by the lowering 

 of the ocean-level. 



Professor Eduard Suess introduced quite new ideas into the 

 discussion of secular movements. In 1875, i n ms work on the 

 origin of the Alps, he attributed the elevation of the Scandi- 

 navian Peninsula to the upward arching of a wide fold ; but in 

 later works, when he entered into a full and critical treatment 

 of the whole question, he came to the conclusion that there 

 were no movements of the crust in vertical senses, with the 

 exception of those which are accomplished indirectly in the 

 course of crust-folding. Suess then proposed a neutral termin- 

 ology to express changes of level; instead of "elevation" and 

 "subsidence" he now speaks of "positive" movements when 

 a coast-line appears to rise, and " negative " movements when 

 it appears to sink. His first elucidation of these views in 1880 

 culminated in the statement that the phenomena of so-called 

 secular upheaval and depression had their origin in continuous 

 changes in the liquid envelope of our globe. Suess could 

 offer no explanation of those changes, which sometimes at one 

 period might amass the ocean-water towards the equatorial 

 zones, at another withdraw it towards Polar regions. He indi- 

 cated as a possibility that they might have some connection 



