830 



POPULAR SCIENTIFIC LECTURES. 



and formed it into a flat disk. From time to 

 time masics at the circumference of this disk 

 became detached under the influence of the 

 increasing centrifugal force ; that which be- 

 came detached formed again into n rotating 

 nebulous mass, which either simply con- 

 densed and formed a planet, or during this 

 condensation again repelled masses from the 

 periphery, which became satellites, or in one 

 case, that of Saturn, remained as a coherent 

 ring. In another case, the mass which sep- 

 arated from the outside of the chief ball, di- 

 vided into many parts, detached from each 

 other, and furnished the swarms of small 

 planets between Mars and Jupiter. 



Our more recent experience as to the na- 

 ture of star showers teaches us that this pro- 

 cess of the condensation of loosely diffused 

 masses to form larger bodies is by no means 

 complete, but still goes on, though the traces 

 are slight. The form in which it now ap- 

 pears is altered by the fact that meanwhile 

 the gaseous or dust like mass diffused in 

 space had united under the influence of the 

 force of attraction, and of the force of crys- 

 tallization of their constituents, to larger 

 pieces than originally existed. 



The showers of stars, as examples now tak- 

 ing pluce of the process which formed the 

 heavenly bodies, are important from another 

 point of view. They develop light and heat ; 

 and that directs us to a third series of con- 

 siderations, which leads again to the same 

 goal. 



All life and all motion on our earth is, with 

 few exceptions, kept up by a single force, 

 that of the sun's rays, which bring to xts light 

 and heat. They warm the air of the hot 

 zones, this becomes lighter and ascends, 

 while the colder air flows toward the poles. 

 Thus is formed the great circulation of the 

 passage - winds. Local differences of tem- 

 perature over land and sea, plains and moun- 

 tains, disturb the uniformity of this great 

 motion, and produce for us the capricious 

 change of winds. Warm aqueous vapors 

 ascend v/ith the warm air, become condensed 

 into clouds, and fall ia the cooler zones, and 

 upon tho snowy tops of the mountains, as 

 rain and as snow. The water collects in 

 brooks, in rivers, moistens the plains, and 

 makes life possible ; crumbles the stones, 

 carries their fragments along, and thus works 

 at the geological transformation of the earth's 

 surface. It is only under the influence, of 

 the sun's rays that the variegated covering of 

 plants of the earth grows ; and while they 

 grow, they accumulate in their structure 

 organic matter, which partly serves tho whole 

 animal kingdom as food, and serves man 

 more particularly as fuel. Coals and lignites, 

 the sources of pcwer of our steam-engines, 

 are remains of primitive plants, the ancient 

 production of the sun's rays. 



Need we wonder if, to our forefathers of 

 the Aryan race in India and Persia, the sun 

 appeared as the fittest symbol of the Deity ? 

 They were right in regarding it as the giver 

 of all life as the ultimate source of almost 

 11 that has happened on earth. 



But whence does tho sun acquire thla 

 force ? It radiates forth a more intense light 

 than can bo attained with any terrestrial 

 means. It yields as much heat as if 1500 

 pounds of coal were burned every hour upon 

 each square foot of its surface. Of tho heat 

 which thus issues from it, tho small fraction 

 which enters our atmosphere furnishes a 

 great mechanical force. Every steam-engine 

 teaches us that heat can produce such force. 

 The sun, in fact, drives on earth a kind of 

 steam - engine whose performances are far 

 greater than those of artificially constructerl 

 machines. The circulation of water in the 

 atmosphere raises, as has been said, tho 

 water evaporated from the warm tropical 

 seas to the mountain heights ; it is, as it were, 

 a water-raising engine of the most magnifi- 

 cent kind, with whose power no artificial 

 machine can bo even distantly compared. I 

 have previously explained the mechanical 

 equivalent of heat. Calculated by that 

 standard, the work which the sun produces 

 by its radiation is equal to the constant ex- 

 ertion of 7000 horse-power lor each square 

 foot of the sun's surface. 



For a long time experience had impressed 

 on our mechanicians that a working force 

 cannot be produced from nothing ; that it 

 can only be taken from the stores which na- 

 ture possesses ; which are strictly limited, 

 and which cannot be increased at pleasure 

 whether it be taken from the rushing water 

 or from tho wind ; whether from the layers 

 of coal, or from men and from animals, 

 which cannot work without the consumption 

 of food. Modern physics has attempted to 

 prove the universality of this experience, to 

 show that it applies to the great whole of all 

 natural processes, and is independent of the 

 special interests of man. These have been 

 generalized and comprehended in the all- 

 ruling natural law of the Conservation of 

 Force. No natural process, and no series of 

 natural processes, can be found, however 

 manifold may be the changes which take 

 place among them, by which a motive force 

 can be continuously produced without a 

 corresponding consumption. Just as tho 

 human race finds on earth but a limited sup- 

 ply of motive forces, capable of producing 

 work, which it can utilize but not increase, 

 so also must this be the case in the great 

 whole of nature. The universe has its definite 

 store of force, which works in it \inder ever- 

 varying l<>nas ; in indestructible, not to be 

 i ; ; . n -JIM < I, everlasting and unchangeable like 

 mutter itself. It seems as if Goethe had an 

 idea of this when he makes the earth-spirit 

 speak of himself as the representative of 

 natural force. 



In the current* of life, in the tempests of motion, 

 lu tho ii.-rvor f nrt. in the fire, in the storm, 



liithcr and thilher, 



'Her und under. 



Wend 1 and wander. 



Jiinh and the grave, 



LtanltlaM ocean, 



Where the restless wave 



Undulates ever 



Under and over. 



Their seething utrifo 



