392 NATURAL HISTORY. 



etc., not only prove characteristic of the different periods 

 at which they have existed, but also prove the truth of 

 those great geological convulsions which have brought 

 the earth to its present form. Through the repetition of 

 these volcanic eruptions, at different epochs and in 

 unequal intervals of time, the firm land gradually sepa- 

 rated more and more from the water, although it does 

 not appear that genuine mountains as yet existed ; but 

 (as geologists say), that the earth's crust, remaining for a 

 long time, at first, in a soft or pasty condition, gradually 

 cooled and became hard, partly by the action of the air 

 and partly by the operations of its own internal agents, 

 as exhibited in volcanic disturbances ; it solidified into 

 masses, and formed what the German geologists term 

 Flotzgebirge, Germ, (stratified mountains), primary 

 rock formation.* 



As each of these stratified formations present us with 

 the traces of the existence of living beings peculiar to 

 the different epochs at which they lived, we have come 

 to the conclusion that at each geological convulsion these 

 animals must have perished by some sudden catastrophe ; 

 and not only is this supposition educed from the posi- 

 tions in which they are found entombed as in the very 

 act of moving, but also that the hard portions of the 

 original structure, such as bones, shells, etc., altered in 



* The word rock, as used by geologists, is applicable to all mineral 

 masses, and includes in its meaning sand, marble, clay, granite, etc., 

 that cover the solid parts. Comparing the different materials com- 

 prising fce earth's crust, as found in examining the excavated side of 

 a mountain, the observer will very soon perceive that there are a 

 great many different formations, and that these layers or stories are 

 in layers or stories reposing one above another (plural of stratum 

 a Latin word, meaning a bed, couch, or layer). RUSCHEV. GEOLOGY. 

 Tr. 



