llesozoic and CcBuozoic Geology and Palceo^itology. 5 



"As we do not comprehend either the creation or annihilation of 

 matter, by the origin of rocks, we mean the last change which pro- 

 duced their present form, and the agents that nature employed to give 

 them that form, or effectuate that change." 



He divided the rocks into three classes (not, however, without ex- 

 pressing grave doubts as to the correctness of his conclusions), as 

 follows : 



1st Class — of Neptunian origin. 1st Order: Sand beds. Gravel beds, 

 Sea salt, Sandstone, Pudding-stone, Brown coal, Bog Iron ore, Calcare- 

 ous tufa. Calcareous depositions, and Silex from hot springs. 



2d Order, resembling in structure, position or component parts, the 

 1st order, the evidence of their origin resting on direct and positive an- 

 alogy: Coal, Gypsum, Chalk, Compact limestone, Sandstone, Pudding- 

 stone, Rock-Salt, Old Red Sandstone, Graywacke and Graywacke slate. 

 Transition sandstone, Transition limestone. Transition g3^psum. Tran- 

 sition cla3'slate. Anthracite and Siliceous schist. 



2d Class — Volcanic origin. 1st Order, thrown out of active volca- 

 noes, and resting on the evidence of our senses: Compact lava. Porous 

 lava, Porphyritic lava. Scoria, Mud lava, Obsidian or Volcanic glass, 

 Pumice-stone and cinders. 



2d Order, resembling the 1st order in structure, position, and com- 

 ponent parts, having the remains of craters, with currents of lava di- 

 verging from them; though the fire which may have formed them is 

 now extinct, the evidence of their origin resting on direct and positive 

 analogy: Basalt, Trap formation called by Werner the newest fleets 

 Trap formation, Pitchstone, Pearlstone, Porphyry' attending the trap 

 as above, and Clinkstone. 



3d Order, where the rocks resemble the second in texture and com- 

 ponent parts, but the proof of their origin resting on a more distant 

 analogy: Basalt, Trap, Pitchstone, Porphyry, and Clinkstone. 



3d Class — the origin doubtful, resembling a little, the 2d order of 

 the 1st and 2d classes, but the analogy neither direct nor positive, 

 amounting only to probable conjecture. 1st Order: such rocks as 

 probable conjecture would incline to place in the Neptunian origin: 

 Gneiss, Mica slate, Clay slate. Primitive slate and limestone. 



2d Order, such rocks as probable conjecture would incline to place 

 in the volcanic origin: Hornblende, Porphyry, Greenstone, Sienite and 

 Granite. 



The greatest good that this author accomplished ma}^ have resulted 

 from constantly teaching that it is through observation, and not through 

 the imagination, that a knowledge of Geology can be acquired. He said : 



