NATURE AS DRAMA AND ENGINERY. 503 



demonstrated that light and electricity differ from each other 

 only as short waves differ from long ones ; presumably the same 

 medium serving as the vehicle for both. His masterly experi- 

 ments thus disclosed another bridge between modes of motion 

 which less than a century ago were accounted distinct and un- 

 connected. 



While the establishment of the truth of the conservation of 

 energy justly ranks among the grandest achievements of human 

 thought, that truth would be rounded into satisfying complete- 

 ness were it proved that energy in all its forms is motion and 

 nothing else. The obstacle here is that gravity does not lend 

 itself to any kinetic theory thus far framed. And this notwith- 

 standing that atomic weight is the fundamental characteristic of 

 matter, so that, indeed, it conditions every property of a sub- 

 stance proof of which arrived in the fulfillment of the predic- 

 tions of Mendelejeef, who, taking this theory as his finder-thought, 

 foretold that scandium, gallium, and germanium would be added 

 to the list of chemical elements, and would be found to possess 

 properties which he detailed. Gravity is marked off from other 

 phases of energy by two characteristics if it be transmitted 

 through space as are other modes of motion, it either travels 

 instantaneously, or so fast as to elude the observation of astrono- 

 mers competent to detect its movement were it fifty million times 

 as swift as light. Quite as remarkable is the fact that a mass 

 may be heated, electrified, magnetized, or chemically transformed 

 without its weight being affected in the slightest degree. This in 

 striking contrast with the action of heat, which modifies the color, 

 chemical activity, conductivity, and other properties of a sub- 

 stance, and its volume as well. The only analogy which gravity 

 bears to other forms of energy is that which it sustains to elec- 

 tricity and magnetism, and were these forces attractive only, the 

 analogy would be a close one. But let us trace what analogy 

 there is and we may find it helpful. In the manufacture of a 

 common steel magnet the palpable motion of a dynamo disap- 

 pears to create its attraction ; the imparted dynamo-motion there- 

 fore is imagined as continuing in full actuality in the molecules 

 of the magnet. When an armature is brought within the mag- 

 net's field it is attracted that is, it powerfully tends to move 

 toward the magnet ; until that impulse is satisfied a space divides 

 armature and magnet. All the analogies of light and electricity, 

 proved to be fundamentally one with magnetism, bid us believe 

 that between magnet and armature a medium is actively con- 

 cerned in bringing both masses together ; why may not a similar, 

 or that identical, medium be active in bringing from a tree an 

 apple to the earth ? What is needed here is investigation of how 

 the motion of a molecule in its own orbit, or on its axis, becomes 



