Related Geological Conditions 37 



Now the writer has watched through successive days, the 

 changes effected in fishes that have been thrown up, and have 

 become high and dry along the shore-lines of marine areas. 

 He has also noted along estuarine banks, over lake margins, 

 and to a less extent though with sufficiently informing out- 

 come, over the floodplains of rivers and streams where fishes 

 had been stranded, likewise in two notable instances along 

 streams where thousands of fishes had been poisoned by 

 chemical products thrown out from mills along the banks. 

 In all cases within eight to ten days nearly every trace of 

 these had been destroyed, by the joint softening, disintegra- 

 ing and mechanical action of rain, dew, bacteria, small 

 crustaceans, insect larvae and higher animals. Rarely one 

 can note a gradual but yet sufficient deposit of mud, sand 

 or lime that can cover and conserve the firmer parts while 

 the softer decay. 



VI. Volcanic dust and the preservation of organisms. 



Even if we accept the action of the above agencies, 

 some more rapid, widespread, and perfect mode of destruc- 

 tion, enclosure and permanent preservation of fishes, as 

 well as other organisms, seems to be called for, as an im- 

 portant geologic and palaeontologic factor. Mention has 

 already been made of wide-spread volcanic action during 

 palaeozoic times. And though less violent and extensive, 

 according to present knowledge in its surface manifesta- 

 tions, this action was continued into mesozoic and more 

 recent periods with at times cataclysmic results. 



Now nearly all of the historic and cataclysmic volcanic 

 outbreaks of the past two hundred years have been ac- 

 companied by copious discharges of poisonous gases, by 

 upheavals or explosions amid terrestrial, lacustrine, and 

 marine strata that mechanically have caused widespread 

 death of organisms over thousands of square miles. In 

 nearly every case also there have been shot into the air 

 enormous quantities of fine volcanic dust of varying com- 

 position, that became redeposited as beds which have varied 

 from seldom less than an inch to one hundred feet or more 

 in thickness. 



