ii2 POPULAR SCIENCE MONTHLY 



FLORISSANT; A MIOCENE POMPEII 



Bx Phofessob T. D. A. COCKERELL 



UNIVERSITY OF COLOEADO 



IN" attempting to trace the evolution of plants and animals, the 

 naturalist finds himself continually regretting what is called 

 " the imperfection of the geological record." Of all the creatures 

 which have lived and died upon the earth, only a very small propor- 

 tion have left any record in the rocks ; and since the remains are widely 

 scattered and belong to very diverse periods of time, anything like a 

 complete consecutive series is usually unattainable. It is somewhat 

 as though the student of languages of some future age might be obliged 

 to depend for his knowledge of the English tongue upon small frag- 

 ments of the pages of Webster's Dictionary, perhaps about an inch 

 square for each page. He would gather his precious scraps together, 

 and by diligently comparing them, would readily deduce a number of 

 things about the construction of the language. He would feel able to 

 restore, in some measure, a certain proportion of the missing words, 

 forming derivatives according to the rules he had been able to ascer- 

 tain. But how he would long for a single complete page ! — for a 

 single series actually presenting to him the different modifications and 

 amplifications of some root in all their richness and variety. 



Each year witnesses an increasing number of paleontological dis- 

 coveries, so that the incomplete series in our museums are gradually 

 becoming more complete and more representative of the actual course 

 of evolution. In some well-known instances, such as those of the horse 

 and elephant groups, the successive stages are now so well known that 

 it is not very difficult for imagination to supply the connecting links; 

 but in others the record is either a total blank or a miserable scrap 

 merely sufficient to awaken curiosity. Take, for instance, the butter- 

 flies. According to Dr. D. Sharp, the living species of butterflies 

 known to science number about 13,000, while it is not impossible that 

 30,000 or even 40,000 actually exist. Butterflies form such a large 

 and varied group, spread over nearly every part of the world where 

 vegetation grows, that it is certain that they have a long history behind 

 them, and that the total number of forms which have existed must run 

 into the hundreds of thousands. Yet the actual number of fossil but- 

 terflies so far discovered is only twenty-two ! Even this meager figure 

 is in a sense an exaggeration, inasmuch as many — indeed most — of the 



