98 ESSAY ON CLASSIFICATION 



family, each genus, each species a different one, and different ones 

 for all successive geological epochs. Phosphate of lime in palasozoic 

 rocks is the same phosphate, as when prepared artificially by Man; 

 but a Fish makes its spines out of it, and every Fish in its own way; 

 Turtles their shield. Birds their wings, Quadrupeds their legs, and 

 Man, like all other Vertebrates, his whole skeleton; and during each 

 successive period in the history of our globe these structures are dif- 

 ferent for different species. What similarity is there between these 

 facts? Do they not plainly indicate the working of different agencies 

 excluding one another? Truly the noble frame of Man does not owe 

 its origin to the same forces which combine to give a definite shape 

 to the crystal. And what is true of the carbonate of lime is equally 

 true of all inorganic substances; they present the same characters in 

 all ages past as those they exhibit now. 



Let us look upon the subject in still another light, and we shall 

 see that the same is also true of the influence of all physical causes. 

 Among these agents the most powerful is certainly electricity; the 

 only one to which, though erroneously, the formation of animals has 

 ever been directly ascribed. The effects it may now produce it ha§ 

 always produced, and produced them in the same manner. It has 

 reduced metallic ores and various earthly minerals and deposited 

 them in crystalline form, in veins, during all geological ages; it has 

 transported these and other substances from one point to another 

 in time past, as we may do now in our laboratories under its in- 

 fluence. Evaporation upon the surface of the earth has always pro- 

 duced clouds in the atmosphere, which after accumulating have been 

 condensed in rain showers in past ages as now. Rain drop marks in 

 the carboniferous and triassic rocks have brought to us this testimony 

 of the identity of the operation of physical agents in past ages, to 

 remind us that what these agents may do now they already did in the 

 same way, in the oldest geological times, and have done at all times. 

 Who, in the presence of such facts, could assume any causal connec- 

 tion between two series of phenomena, the one of which is e\'er obey- 

 ing the same laws, while the other presents at every successive period 

 new relations, an ever changing gradation of new combinations, lead- 

 ing to a final climax with the appearance of Man? Who does not see, 

 on the contrary, that this identity of the products of physical agents 

 in all ages totally disproves any influence on their part in the pro- 



