Missing Chapters of Geological History. 15 



tinuous accumulation on a sea-bottom. That the depth, the 

 nature of the material, the distance from the shore, the extent 

 of life, development, and various other matters may have 

 remained similar during similar accumulations, but was liable to 

 change, and did constantly change, there can be no doubt. 

 Such is the nature of all sea-bofctoms now, and such must have 

 been the case more or less through all time. Each principal 

 formation thus represents thousands of sea-bottoms piled regu- 

 larly one over another, slowly perhaps, and with occasional 

 interruptions and slight changes of condition. During all this 

 time other parts of the sea were receiving deposits. These no 

 doubt were most like each other over a large area when the 

 conditions were the same. The temperature of deep water is 

 more uniform, the water is more still, the interruptions less 

 considerable. "Where then we find very wide areas and thick 

 series of rocks very uniform in their nature and in the fossils 

 contained, we may fairly assume the lapse of a long period, 

 during which change was gradual. 



On the other hand, where elevation or depression occurred, 

 the conditions producing modifications of organic forms are pre- 

 sent, and would be easily traceable. Where a great and 

 important change occurred, such as the elevation of a con- 

 tinent with its mountain chain, we might well expect that the 

 change should be total and extreme. 



When now we pass in review the various deposits, bearing 

 in mind these general conclusions, and assuming that the series 

 is imperfect, but that whatever it indicated, whether directly 

 or by inference, is not only truth but systematic truth, we shall 

 see some light thrown on the great question of geological 

 succession. 



Commencing with the older or Palseozoic group of rocks, as 

 developed in England, we find four recognized divisions in the 

 established books on geology, known respectively as Silurian, 

 Devonian, Carboniferous, and Permian. There are others 

 recently introduced, but these we will speak of presently. Of 

 these four it has generally been supposed that very few species 

 are common to any two, and scarcely any to three. All forms 

 of Silurian life are supposed to have vanished long before the 

 end of the Carboniferous period, and breaks or strongly-marked 

 interruptions, marking the lapse of long periods, are supposed 

 to have occurred between the end of each one deposit and the 

 beginning of the next. It is important that there should be a 

 distinct notion as to the value of this idea. It lies at the base of 

 many generalizations that require revision. It represents the 

 belief of the paroxysmal school of geology, adopting and en- 

 forcing the idea that a special creation was required for each 

 species of animal and vegetable, and that special groups of 



