Conversations on Geology, 4?65 



a long course of years, be crumbled down, or, as the geologists say, disin- 

 tegrated, and gradually carried by rivers, in the form of sand, clay, and 

 gravel, to the sea. At the bottom of the sea these materials would arrange 

 themselves in beds, differing in thickness, according to the circumstances by 

 which they might be affected. But those beds would have continued in the 

 soft state of sand or clay for ever, unless something occurred to harden 

 them. It is here that Dr. Hutton brings in the agency of fire, and tells us, 

 that there is at the bottom of the sea sufficient heat, from a great central 

 fire which he conceives to exist in the centre of the globe, to melt all the 

 clay, sand, and gravel, and to form them into rocks. He provides for the 

 appearance of these above water, by supposing that the central fire occa- 

 sionally expands itself, and elevates the newly formed rocks into islands and 

 continents, diversified by hills and vallies ; these being destined in their 

 turn to the same changes of destruction and renovation, as those from which 

 they took their origin.' (p. 47 — 50.) 



* According to the rival geological theorist, Werner, all the substances 

 which now constitute rocks, mountains, and soil on the earth's surface, were 

 originally existing, in a state of solution, in the waters of the great chaos, 

 which he supposes at the beginning to have surrounded the globe to a vast 

 depth. The substances or materials of rocks, thus swimming in the primi- 

 tive ocean, he conceives to have gradually fallen to the bottom, sometimes 

 by chemical, sometimes by mechanical means, and sometimes by both to- 

 gether ; and in this manner, he thinks, all the rocks have been formed which 

 we now find on digging into the earth. The inequalities of mountains and 

 vallies on the surface of the earth, which were thus produced as soon as the 

 waters began to subside (and this subsidence is an important point in the 

 system), gradually rose out of the primitive sea, forming the first dry land. 

 The rocks which were in this manner first formed, Werner calls the Ori- 

 ginal or Primitive Formation : they consist of granite, gneiss, different species 

 of slate, marble, and trap. 



* The formation of these rocks, however, did not, it seems, exhaust the 

 materials floating in the waters, for the deposition went on, and a class of 

 rocks were formed consisting of grey wack^ limestone, and trap, which 

 rested on the primitive, and are called by Werner the Jntermediate or 

 Transition Rocks, because, on their appearance above the waters, the earth, 

 he conceives, passed into a habitable state. 



* After the formation of those primitive and transition rocks, Werner 

 alleges that the water suddenly rose over them to a great height, covering 

 them in many places, as it again subsided, with a new formation of rocks, 

 consisting of sandstone, conglomerates, limestone, gypsum, chalk, and rock-, 

 salt, which he called Level or Floetz Rocks. 



* Since that period, the wearing down of the rocks, by the action of the 

 weather and other causes, and the washing away of the worn materials by 

 rains and streams of water, have formed soil, gravel, sand, peat, and the 

 various other beds which are called Alluvial' (p. 58 — 60.) 



Into the details of these two systems, and the numerous 

 objections to their several opinions, started and explained in 

 the Conversations, we have not room to enter; and much less 

 can we take up at present the still more rational and plau- 

 sible system which Mr. Granville Penn has constructed from 

 the Mosaic history of the creation and the deluge, and which 

 is also fully treated of in the latter part of the volume. Our 

 readers, however, may like to see a list of the subjects treated 

 of in their order : these are, " Theories of the earth ; Geolo- 



