410 COSMIC nilLOSOriJY. [r-r. 11. 



from the dense atmosphere, and incorporating it in the tissues 

 of innumerable forests. Charred by slow heat, and gradually 

 petrified, this woody tissue became transformed into coal, 

 which now, dug up from its low-lying beds and burned in 

 stoves and furnaces, is compelled to give up the radiance 

 which it long ago purloined from the sun. "When placed 

 under the engine boiler, these transformed sunbeams are 

 again metamorphosed into molar motions of expanding 

 vapour, which cause the rhythmic rise and fall of the piston, 

 and drive the running-gear of the machine-shop or propel 

 the railway-train. In such wise it may be shown that the 

 various agencies which man makes subservient to industrial 

 purposes, are nothing but variously differentiated sunbeams. 

 The windmill is driven by atmospheric currents which the 

 sun set in motion. The water-wheel is kept whirling by 

 streams raised by the sun to the heights from which they 

 are rushing down. And the steam-engine derives its energy 

 from modern or from ancient sunbeams, according as its fires 

 are fed by wood or by coal. 



But the solar energy stored up by vegetables is given out 

 not only in such mechanical processes, but also in the vital 

 activities of the human beings whose needs such processes 

 supply. The absolute dependence of animal upon vegetal 

 life is illustrated in the familiar fact that animals cannot 

 directly assimilate inorganic compounds. The inorganic 

 water which we drink is necessary to the maintenance of 

 life; but it percolates untransfoimi'd through the tissues and 

 blood-vessels, and it quits the organism in the same chemi- 

 cal condition in which it entered it. And although minute 

 quantities of the salt which we daily eat, and of the car- 

 bonates and iodides of iron which we sometimes take as 

 tonics, may perhaps undergo transformation in the tissues ; 

 it is none the less true that the substance of our tissues can 

 only be repaired by means of the complex albuminous mole- 

 cules which solar energy originally built up into the tissues of 



