308 SPARKS FROM A GEOLOGIST'S HAMMER. 



series of forms representative of a series of ideas, and 

 these sustain an evolutionary relation to each other in 

 each series. These forms have evidently been evolved 

 generatively. How else should they be found consecu- 

 tive? The ancestors of the horse are found in Pttohip- 

 pus, Mesolrippus and Orohippus,* and it seems quite as 

 clear that the saw-log is the great-great-great-grandfather 

 of the brig. Thus the ship, which rolls like a log (hence 

 its 'record is called a " log-book "), has inherited an an- 

 cestral trait, like the man with a sharp tip to his ear. 

 Now, jf the reader has followed me to this point with- 

 out being convinced, I desire him to follow me on an- 

 other departure. Just as the Ascidian from which man 

 is descended, presented, in the course of generations, di- 

 vergences which became class-types, viz., fishes, reptiles, 

 birds and mammals, so the ascidian ship, in the course 

 of generations, has developed three classes of vessels, viz , 

 rowing-vessels, wind-vessels, and steam-vessels. The row- 

 ing-vessels answer to the sluggish reptiles; the sailing- 

 vessels are probably birds, and the steam-vessels are New 

 Yorkers, of whom the Chicagoan is .clearly a more fully 

 developed species. It is probable that the vessels answer- 

 ing to the class of fishes are those like * monitors," 

 " steam-rams," or torpedo-boats, or, perhaps, like those 

 Atlantic passenger steamers which go under water. But 

 I leave the fish-ships out of the argument. Now, I have 

 shown that the genera and species of the rowing-class 

 sustain genetic relations to each other, and that those 

 of the sailing-class sustain similar relationships to each 

 other and to the rowing-class. A few words will show 

 that this relationship runs through the steam-class, and 

 thus the whole subkingdom of water-craft. Look at the 



