ANIMALS EXTINCT IN THE HISTORIC PERIOD. 331 



And again, they will render valuable aid to the science of meteor- 

 ology. We have as yet no knowledge of the constants of evaporation 

 from water-surfaces. On this point the Edinburgh Reviewer remarks : 

 "An unusually favorable opportunity now presents itself for the actual 

 determination of the most steady and remarkable case of evaporation 

 that occurs on the surface of our planet. In its headlong course from 

 the foot of Ilermon, the Jordan (well named the descender) may al- 

 most be said to consist of tiiree continuous cataracts, divided by two 

 lakes and terminating in a third. From the surface of that bituminous 

 sea, the whole supply brought down by the Jordan and its affluents 

 is exhaled in invisible vapor. By an accurate measurement of the 

 volume discharged by the Jordan, we shall be furnished with evapo- 

 rative data of the hisrhest value." 



ANIMALS EXTINCT IN THE HISTOEIC PEEIOD. 



By EMILE BLANCHAKD. 

 translated from thk revue des deux moxdes, by a. r. macdonough, 



ALL beings are exposed to more or less frequent dangers, and are 

 constantly struggling to defend their lives. They have to dread 

 the inclemency of the seasons, and must perish if they fail to find a 

 sufficiency of food ; the herbivorous are destined to become a prey to 

 the carnivorous, and, when there seems no need of a victim, deadly 

 battles occur for the possession of a place or the conquest of a prize. 

 Destruction is a natural law ; but this destruction is restrained within 

 certain limits: notwithstanding tlie perils that incessantly threaten 

 the existence of all creatures, every thing works actively to secure the 

 maintenance of races. That instinct of preservation which goads 

 individuals to fly from danger and seek the satisfaction of their mate- 

 rial wants, allows many to escape accidents. If the causes of violent 

 death vary within the widest range among animal species, they are 

 always proportioned to the causes that protect against it. Fecundity, 

 restricted among powerful animals, and limited also in those that have 

 only the attacks of the strongest to fear, is prodigious among the 

 weakest that are doomed to yield a multitude of victims. Thus the 

 complete disappearance of any species is only possible under wholly 

 exceptional conditions. Usually, the species destroyed at one point 

 continues to propagate itself at another: if abundant at one period, it 

 is rare at another, when circumstances become unfavorable ; yet it has 

 not ceased to be represented, in some corner of the world. Certainty 

 in this respect has been gained by exact and very numerous observa- 

 tions. Since the day when the last grand physical phenomena were 



