Ex.—Lay a magnet down on iron filings. They will gather in greatest abundance about the poles, and diminish toward the center, where there are none; thus showing the nature of polarity.
Energy often disappears to reappear under a different name. If we lift our hand to strike the palm of another, our vital energy becomes motion, and that in turn is changed into heat.
In the Bell telephone the sound-waves in the mouthpiece are converted into electric vibrations in the wire, and these, in turn, induce sound-waves in the receiving instrument at the other end of the line.
In dynamo-electric machines we have a chain of transmutations of force—chemical affinity in the fire-box, expansion in the boiler, becoming in turn, motion, magnetism, electric currents, until it appears as resplendent light and intense heat between the carbon points.
Potential energy slumbers in the raindrop, and, anon, as kinetic energy, flashes in the lightning.
In short, the sum of all the energies of nature is a constant quantity, although it manifests itself in a thousand different ways. The foregoing reflections indicate that the researches of modern science all point to a grand unity in God’s universe. Let us conclude by briefly referring to some instances of plan or design in the
GROUPING OF LAWS.
The most characteristic feature of all science is that it arranges facts in an orderly manner, under principles or laws.
Nature seems to delight, likewise, in doing a variety of things under one general principle. Note a curious trinity in her method: We have three great departments of nature—animal, vegetable and mineral; three parts to our being—physical, mental and moral; three divisions of the mind—intellect, sensibilities and will; three parts to all plants—root, stem and foliage; there is earth, sea and sky; three great classes in all mechanism—lever, cord, and inclined plane—and many others that might be mentioned.