THE I.I M ITS OF SCIENCE 



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to be reached by optical instruments; she has calculated the 

 actual size of the atoms, or individual units of which the elemen- 

 tary, or for that matter, all bodies, are composed; she tells us, 

 for instance, that one of these atoms compared to a drop of 

 water, is no larger than a rifle bullet compared to the whole 

 earth, their size being the thousand millionth of an inch in 

 diameter. We are told that they are constantly in motion, and 

 in solids, constantly colliding with each other; in ordinary air the 

 motion is not regular, but consists of zig-zag paths, each straight 

 portion being so short that it is on an average ultra-microscopic, 

 rid each atom strikes another about six thousand million times 

 a second. The layman might. 1 think, at this stage, be excused 

 if he ventured to enquire satirically of the professor of science 

 if he does not bud the atoms somewhat too coarse, and if he 

 would not recommend their undergoing a sti'll finer powdering 

 up process. The question, however, might just as well be 

 asked seriously, for the so-called " Electron Theory " has now 

 been generally accepted in scientific circles. From it we learn 

 that the atoms, so far from being, as was previously supposed, 

 the smallest and indivisible parts of matter, are actually only 

 the gathering places of still smaller bodies. We might compare 

 them to systems of suns, round with planets, or electrons, of 

 considerably smaller dimensions, revolve. More, indeed, is now 

 known of these electrons than of the atoms themselves, and the 

 theory of their existence and movements explains so completely 

 various phenomena of electricity, gas discharges, radium rays, 

 spectroscopy, and chemical affinity, which were before inex- 

 plicable, that the theory may now be considered to be as firmly 

 established in dealing with matter within the molecular, or 

 atomic, range, as the Copernican theory is. in dealing with the 

 heavenly bodies. Not only are we told the number of electrons 

 per atom, we are told that they all weigh the same amount, and 

 also that they are all alike in size. It is known that an atom is 

 one thousand millionth of an inch in diameter, therefore, taking 

 the comparison between the sun and the earth to be true for the 

 atom and electron, as it actually is. at any rate comparing their 

 masses, approximately for the heavier metals, the electron must 

 have a diameter of about a hundred thousand millionth of an 

 inch. The length of time taken by electrons to complete their 

 orbits round their atoms varies considerably, and this matter 

 is of importance to us, because the various effects of electricity, 

 heat and colour, or light, are affected by it. If the electrons have 

 what are for them relatively very long years, i.e., if they com- 

 plete only a few hundred million revolutions in a second, the kind 

 of ether waves used in wireless telegraphy are produced ; if they 

 move more rapidly the matter of which they are composed will 

 give out dark heat ether waves; if they complete their orbits 

 still more speedily, say at the rate of 400 billions per second, 

 the matter of which they are constituted will give out a red 

 heat, and with still shorter electron years the various colours will 



