128 Things not generally Known. 



celebrated classification of which he is the sole author, and by 

 which fossil ichthyology has for the first time assumed a precise 

 and definite shape. How essential its study is to the geologist 

 appears from the remark of Sir Roderick Murchison, that "fos- 

 sil fishes have every where proved the most exact chronometer 

 of the age of rocks." 



SUCCESSION OF LIFE IN TIME. 



In the Museum of Economic Geology, in Jermyn Street, may 

 be seen ores, metals, rocks, and whole suites of fossils strati- 

 graphically arranged in such a manner that, with an observant 

 eye for form, all may easily understand the more obvious scien- 

 tific meanings of the Succession of Life in Time, and its bearing 

 on geological economies. It is perhaps scarcely an exaggeration 

 to say, that the greater number of so-called educated persons 

 are still ignorant of the meaning of this great doctrine. They 

 would be ashamed not to know that there are many suns and 

 material worlds besides our own ; but the science, equally grand 

 and comprehensible, that aims at the discovery of the laws that 

 regulated the creation, extension, decadence, and utter extinc- 

 tion of many successive species, genera, and whole orders of life, 

 is ignored, or, if intruded on the attention, is looked on as an 

 uncertain and dangerous dream, and this in a country which 

 was almost the nursery of geology, and which for half a century 

 has boasted the first Geological Society in the world. Saturday 

 Review, No. 140. 



PRIMITIVE DIVERSITY AND NUMBERS OF ANIMALS IN 

 GEOLOGICAL TIMES. . 



Professor Agassiz considers that the very fact of certain stra- 

 tified rocks, even among the oldest formations, being almost 

 entirely made up of fragments of organised beings, should long 

 ago have satisfied the most sceptical that both animal and 

 vegetable life were as active and profusely scattered upon the whole 

 globe at all times, and during all geological periods, as they are 

 now. No coral reef in the Pacific contains a larger amount 

 of organic debris than some of the limestone deposits of the 

 tertiary, of the cretaceous, or of the oolitic, nay even of the 

 paleozoic period ; and the whole vegetable carpet covering the 

 present surface of the globe, even if we were to consider only 

 the luxuriant vegetation of the tropics, leaving entirely out of 

 consideration the entire expanse of the ocean, as well as those 

 tracts of land where, under less favourable circumstances, the 

 growth of plants is more reduced, would not form one single 

 seam of workable coal to be compared to the many thick beds 

 contained in the rocks of the carboniferous period alone. 



