PRIMARY CONCEPTS OF MODERN SCIENCE, 349 



proceeding from both, that you depart immediately from these fields, or vine- 

 yards, or waters, and dwell in them no longer, but go away to those places in 

 which you can harm no person ; and on the part of the Almighty God, and the 

 whole heavenly choir, and the holy Church of God, cursing you whithersoever 

 ye shall go, daily wasting away and decreasing until no remains of you are found 

 in any place, unless necessary to the health and use of man, which may He 

 vouchsafe to do who shall come to judge the living and the dead and the world 

 by fire. Amen." 



Traveling rapidly and by night, their sudden irruption into a lo- 

 cality, together with the complete destruction of the field and garden 

 crops, tended to make the ignorant peasantry look upon them as a 

 special visitation from Providence for their sins, and will readily ac- 

 count for the extraordinary notions held regarding them. 



Many animals migrate from place to place, or take possession of 

 new territory, when food becomes scarce ; but we have only one other 

 instance of a living creature migrating in vast numbers to certain de- 

 struction, and that is the locust. When their numbers increase be- 

 yond the food-producing powers of their natural habitat, they pour in 

 countless millions into the colder regions beyond, smothering each 

 other in their flight, until the ground is covered with their dead bodies 

 to the depth of several inches, and water-courses are choked up by 

 them, until the air is tainted with the smell of their putrid bodies for 

 miles. None of them ever return whence they came. Their course 

 is always onward, until those that escape death by accident are 

 killed by the first cold weather they encounter. And in this way Na- 

 ture compels, from time to time, a vast body of these creatures to an 

 act of self-destruction in order that the species may not be annihilated. 

 — Abridged from Temple Bar. 



-♦♦♦- 



THE PEIMAEY CONCEPTS OF MODERN PHYSICAL 



SCIENCE. 



By J. B. Stallo. 



IV. — Inertia and Force. 



IF we look for the speculative background of modern physical theo- 

 ries, we find something like this : Originally there was created, or 

 somehow came to be, an indefinite number of absolutely hard and 

 unchangeable particles of matter. There was also created, or somehow 

 came to be, a number of forces, equally unchangeable — the force of 

 attraction, the force of cohesion, heat, electric and magnetic forces, and 

 so on. The forces began to act and continue to act upon the particles 

 of matter, producing inorganic as well as organic forms. These par- 

 ticles and forces are ultimate facts of experience as well as of thought ; 



