434 ORGANIC CHEMISTRY. 



phere by the sun, it descends again in dew and rain, 

 corroding and dissolving the rocks on which it falls, 

 and distributing them widely over land and sea. 



1072. It settles through the stony crust 



What distinct , . . . , , , 



office does it of the earth, into the dark recesses of the 

 fulfil? rocks where crystals blossom out of the 



formless stone, and supplies them with the material 

 for their wonderful architecture. It penetrates the 

 soil, and supplies the same material to the roots of 

 plants for the still more wonderful creations of leaf, 

 and fruit, and flower. Again it hastens through 

 brooks and rivers on its course, and pours its burden 

 into the sea, for the use of the innumerable forms of 

 vegetable and animal life which inhabit its waters. 

 The coral insect builds up solid islands out of the mat- 

 ter it provides. Countless shell-fish clothe themselves 

 in the same rocky garments, and finally cast them aside, 

 to be buried under the slime of the sea and harden, in 

 the course of ages, into stone. The water which has 

 served these various offices, climbs anew into the 

 heavens upon the solar rays, and again descends in 

 the rain, repeating forever its round of service to the 

 earth. 



1073. The further relations of the three 



How may the n L , . 



further reia- kingdoms of nature may be presented in 

 fhrll king- a sm gl e picture. Imagine a giant tree, the 

 doms be i'llus- representative of all the vegetation of the 

 earth, spreading wide its branches as a shel- 

 ter for man and beast. Let us suppose them to subsist 

 entirely upon its fruit, and to warm themselves by fires 

 made from its branches. The tree, through its leaves, 



