378 THE POPULAR SCIENCE MONTHLY. 



equivalent to the requisite liberation of force necessary to reduce the 

 gases back again to the solid form of ice. A cubic foot of water yields 

 1,862 cubic feet of the separate gases when at normal condition, and 

 no human device is competent to overcome this expansion by pressure 

 sufficient to reduce them back again to the liquid condition. Upon the 

 evidence of Faraday we have it that " the decomposition of a single 

 drop of water by electricity calls for an expenditure of more electromo- 

 tive force than would suffice to charge a thunder-cloud." 



Our main source of dynamic energy is from the sun. His energy is 

 exhibited in every wind that blows, in every shower that falls, and in 

 the history of every snow-flake — in the glare of gaslights, in the heat 

 of the furnace, in the colors of the rainbow, and in the gorgeous sun- 

 set, in the beauty of vegetation and its silent growth. Thus, in an 

 almost infinite variety of physical phenomena we see this transmuta- 

 tion of solar energy. This energy, after doing its allotted work, is in 

 time dissipated into space by radiation. And, were it not for the inter- 

 mediate position of the vegetable kingdom to check this degradation 

 of energy and raise the elementary constituents from the chemical to 

 the organic plane, man's duration here would be short indeed. The 

 locking up of potential energy in the protoplasmic cell of the plant 

 requires the expenditure of a vast amount of energy, but the solar ray, 

 aided by the subtile alchemy of the leaf, is competent for the task ; 

 and, while the chlorophyl of the leaf assists in weaving organic tissues 

 from the air, this outward dissipation of energy is delayed for a while, 

 giving us food for our bodies and fuel for our fires. This final process 

 of combustion once more converts these potential energies into the 

 dynamic form and sets them free to dissipate into space. All the me- 

 chanical power which comes from the combustion of fuel and all the 

 muscular force of the animal kingdom is but the transmutation of solar 

 energy through the mediumship of plant -life. "Well might we say, as 

 did the pagans of old, " We are children of the sun." This flood of 

 solar force is unceasing. Waves of ether may conduct a store of ener- 

 gies across the universe and invest them in a wealth of carbonaceous 

 flora ; these energies may lie dormant in vegetable fossils for untold 

 eras ; man may delve in mines and exhume the coal, and enlist the aid 

 of oxygen to break the bonds of chemical affinity, setting free those 

 energies stored away in the countless ages of the past ; he may unfold 

 link after link of the great dynamic chain of causation, and subject 

 them to the scrutinizing analysis of the physicist ; he may survey the 

 rocks and tell us of their radiations of internal heat, or by his calculus 

 tell us for how long in the past this planet may have been the theatre 

 of life and death ; he may tell us, not only of the energies in the 

 atoms of a drop of water, but of a world of atoms — nay, more, of a 

 universe made up of atoms with their energies drifting out into meas- 

 ureless space ; but he can tell us naught of that unseen universe into 

 which the energies of the visible creation are ever tending. 



