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THE POPULAR SCIENCE MONTHLY 



location of it. Our practical working cer- 

 tainty of the existence of matter means : 1. 

 That it offers resistance to our imagination 

 and our will ; and, 2. That it offers absolute 

 resistance to all attempts to change its quan- 

 tity. Certain other things notably energy 

 are in the same sense conserved, and, if 

 we recognize the transmutability of energy 

 of motion into energy of jiosition, we may 

 say that energy is equally indestructible 

 with matter itself. But energy is under- 

 going a perpetual self-degradation. All 

 other forms of energy are slowly passing 

 into invisible heat-motions, and when the 

 heat of the universe has ultimately been 

 equalized, as it must be, all possibility of 

 physical action or of work will have depart- 

 ed. Mechanical effort cannot longer be ob- 

 tained from it. Tlie perfect heat-engine 

 only converts a portion of the heat into 

 work ; the rest is lost forever as an availa- 

 ble source of work. There is indeed a sort 

 of wild and far-off possibility by which a 

 little more work miglit be got out of a uni- 

 form-temperature universe, if we could sup- 

 pose Clerk-Maxwell's demons ' mere guid- 

 ance applied by human intelligence ' occu- 

 pied in separating those particles of a heated 

 gas which are moving faster than the aver- 

 age from those which are moving slower. 

 But this is but a broken reed to trust, and 

 it would at the best avail us little. What 

 must happen in the existing physical sys- 

 tem would be this : the earth, the planets, 

 the sun, the stars, are gradually cooling ; 

 but infinitely numerous catastrophes, by 

 which the enormous existing store of en- 

 ergy of position may be drawn upon, may 

 over and over again restore unequal tem- 

 perature. The fall together, from the dis- 

 tance of Sirius, of tlie sun and another equal 

 sun would supply the former with at least 

 thirty times as much energy as can have 

 been obtained by the condensation of his 

 materials out of a practically infinite nebu- 

 lous mass of stones or dust. But these 

 catastrophes can only delay the inevitable. 

 If the existing physical universe be finite 

 and the authors never seem to realize the 

 speculative possibility that it may not be 

 so the end must come, unless there Ife an 

 invisible universe to supplement and con- 

 tinue it. 



" What is the ultimate nature of matter, 

 and especially of the ether, which is the 

 vehicle of all the energy we receive from 

 the sun? There have been four theories, 

 for each of which something may be said. 

 There is the Lucretian tlieory of an original, 

 indivisible, infinitely hard atom, ' strong in 



solid singleness ; ' Boscovich's theory that 

 the atom or unit is a mere centre of force ; 

 the theory that matter, instead of being 

 atomic, is infinitely divisible, practically 

 continuous, intensely heterogeneous ; and, 

 finally, the theory of the vortex-atom, a thing 

 not infinitely hard and therefore indivisible, 

 but infinitely mobile, so that it escapes all 

 force which makes effort to divide it. What 

 we call matter may thus consist of the ro- 

 tating portions of a perfect fluid, which 

 continuously fills space. Sliould this fluid 

 exist, there must be a creative act for the 

 destruction or production of the smallest 

 portion of matter. Whichever of these 

 theories we adopt, we must explain the 

 simplest affection of matter that by which 

 it attracts other matter. There seems little 

 possibility of doing so. The most plausible 

 explanation is in Le Sage's assumption of 

 ultramundane corpuscles, infinite in number, 

 excessively small in size, flying about with 

 enormous velocities in all directions. These 

 particles must move with perfect freedom 

 among the particles of ordinary matter, and 

 if they do so we can understand how, 

 through the existence of the ultramundane 

 particles, two mundane particles attract in- 

 versely as the square of the distance. On 

 this theory the energy of position is only 

 the energy of motion of ultramundane and 

 invisible particles and a bridge is built be- 

 tween the seen and the unseen. These ul- 

 tramundane particles are something far more 

 completely removed from all possibility of 

 sensible qualities than the ether which Sir 

 William Thomson has attempted to weigh. 

 Struve has speculated upon the possibility 

 that it is not inflnitely transparent to light, 

 and his calculations, based on the numbers 

 of stars of each visible magnitude, lead him 

 to suppose that some portion of the light 

 and energy from distant suns and planets 

 may be absorbed in it. The ether is thus a 

 kind of adumbration or foretaste of the in- 

 visible world. It may have certain 06 the 

 properties of that world which is perceived 

 by sense, but it is probably subject only to 

 a few of the physical conditions of ordinary 

 matter. 



" Let us look once more at the substance 

 of the universe. We recognize that it is im- 

 possible to suppose any existing state but 

 as the development of something preexist- 

 ing. To suppose creation is to suppose the 

 unconditioned. Creation belongs to eter- 

 nity, and not to time. This being so, it ia 

 difficult to believe in the vortex-ring theory, 

 which regards the invisible universe as an 

 absolutely perfect fluid. With an imperfect 



