A. BLTTT. 



climatic alternations may be pretty well fixed; I have found 

 that this number is not quite so great as I formerly supposed, 

 and that the whole series corresponds in a beautiful manner 

 with the curve of the eccentricity of the earth's orbit and in a 

 manner that agrees completely with the palaeontological evidence. 



Besides the more inconstant beds we find in this series 

 others which are very regular and constant. In my researches 

 on the peat mosses, 1 I have shown, that the layers of tree stumps, 

 occurring at intervals in the peat, often divide between peat 

 layers with a different fossil flora. These forest beds, therefore, 

 show that the formation of peat was arrested several times by 

 dry periods of very long duration, since we see that the flora, 

 during these interruptions in the peat building, was more or 

 less changed. In the marine beds the dry periods are predo- 

 minantly represented by chemically formed layers such as 

 banks of limestone, beds of ironstone, layers of septaria etc., 

 whilst, in the rainy periods, the rivers swelled and more or less 

 thick beds of mechanical sediments, as clay, mud, and the like, were 

 deposited. And, as in the peat mosses the forest beds often 

 show a long interruption in the peat forming, so, likewise, do 

 many of these marine and fluviatile chemical beds point to a 

 long interruption in the deposition of mechanical sediments. We 

 often find that limestone banks and layers of septaria divide be- 

 tween mechanical deposits with more or less different faunas 

 and form, thus, a division between stages and substages of the 

 geological series. In the fluvio-marine beds, which form the 

 subject of the present note, we find several such instances as 

 we shall presently see. 



I will now go on to describe, according to Forbes, the main 

 features of the Oligocene beds in the Isle of Wight. 



The Upper Eocene Barton clay has 5 layers of septaria. 

 It is synchronous with the Gres de Beauchamp of the Paris 

 basin and it must consequently, like this, correspond to the 



Blytt: 



