Page:Popular Science Monthly Volume 5.djvu/345

Rh And again, they will render valuable aid to the science of meteorology. 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 Hermon, the Jordan (well named the descender) may almost be said to consist of three 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 evaporative data of the highest value."



LL 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 the 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 material 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 observations. Since the day when the last grand physical phenomena were 