44 Professor Bronn on some Geological and Phi/sical 



fore, have universal well-defined divisions existed in the history 

 of the formation of Neptunian products, nor have marks of 

 such been left for us. This consequence, so very easily de- 

 ducible from the hypothesis of the formation of rocks, was for 

 a long time not drawn, at the period when appearances seemed 

 against it ; and because, in sciences of observation, facts have 

 so frequently overturned conclusions much too hastily formed, 

 and soon afterwards individuals have been so fortunate as to ex- 

 plain the contradictory facts as a necessary consequence of the 

 same hypothesis by means of new kinds of reasoning. When, 

 therefore, I now assert the necessity of giving up the sharp 

 distinction of geological periods, this is not the consequence of 

 a preconceived theoretical opinion, but because the proofs of 

 the opinion are already in existence. 



At no period was the whole surface of the earth entirely 

 sea, and at no period was it entirely dry land or in a marshy 

 state ; but many parts have been often in both conditions for 

 a time or alternately. When a portion was continuously covered 

 by the sea for a period not too short, the deposits then formed, 

 and their contents, would remain of a uniform character, or 

 only gradually become changed. If, in connection with such 

 a state of things, another portion in the vicinity was covered 

 by the sea at the beginning and the end of the period, but 

 was dry the intervening time, there would be an abrupt in- 

 terruption between the two deposits ; in short there would be 

 the same distinction as between the earlier and later deposits 

 of the first mentioned portion, but without the intermediate 

 links. If, in the first region, a violent current destroyed a 

 part of the already formed connecting links, a similar but 

 even more distinct interruption would arise, because the re- 

 maining positive traces of the destruction would become 

 blended together. Events such as the two last, have no doubt 

 occurred on a very great scale over central Europe, and these 

 have given rise to the adoption of the idea of the distinct se- 

 paration of the strata of the crust of the earth into five peri- 

 ods ; perhaps, also, in many cases, the concealment of the ac- 

 tually existing intermediate strata in less opened up depths of 

 the earth has contributed to the belief. Extensive mountain 

 elevations likewise, with a high inclination of strata, on which 



