BLYTT. 



[No. 1. 



In regard to these great transgressions, we must bear in 

 mind that it is only in the folded ranges and in strongly up- 

 heaved regions (e. g. in the Alps, the Himalayas, Colorado etc.) 

 that marine formed beds from the younger and youngest geolo- 

 gical epochs are found at any particularly great height above the 

 sea. Those great upheavals are, if we consider them in relation 

 to the great whole, only to be regarded as quite local pheno- 

 mena. When the beds were formed, they lay far lower down, 

 and when we now find an alternation of marine beds and fresh- 

 water beds in such formations, we must guard ourselves against 

 believing that the ocean rose and fell in relation to the land 

 for thousands of feet at each oscillation. During the period of 

 formation it was only necessary for the beach-line to have oscil- 

 lated a few metres up and down. Afterwards the entire series 

 of layers became upheaved, by locally acting subterranean forces, 

 high above its original level. 



Therefore, I think, that not even do the great transgres- 

 sions imply, in any specially great degree, the displacement of 

 beach-lines in a vertical direction. Where there are extensive 

 lowlands, with basin-formed depressions, a slight rise may be 

 quite sufficient to produce great geographical changes. 



It is also possible that these transgressions may be due to 

 alterations in the eccentricity of the Earth's orbit. 



We will now proceed to test our hypothesis by a comparison 

 of the astronomical periods with the geological series of beds. 



The curve of the eccentricity of the Earth's orbit has 

 been calculated according to Leverrier's formula by J. Groll (Cli- 

 mate and Time. London 1875, p. 312) for a period of four mil- 

 lion years; three millions backwards, and one million forward 

 from the present time. The curve has also been calculated by 

 Mc. Farland, according to the same formulas (Am. Journ. of 

 Science Ser. Ill Vol. XX. New Haven 1880, p. 105). His 



