12^ THE PHYSICAL GEOGRAPHY OF THE SEA. 



runs into the sea (§ 270) may be considered as the excess of the 

 precipitation over the evaporation that takes place in the valley 

 drained by that river. In other parts of the earth the evapora- 

 tion and precipitation are exactly equal, as in those inland basins 

 such as that in which the city of Mexico, Lake Titicaca, the Cas- 

 pian Sea, etc., etc., are situated, which basins have no ocean drain- 

 age. If more rain fell in the valley of the Caspian Sea than is 

 evaporated from it, that sea would finally get full and overflow 

 the whole of that great basin. If less fell than is evaporated from 

 it again, then that sea, in the course of time, would dry up, and 

 plants and animals there would all perish for the want of water. 

 In the sheets of water which we find distributed over that and ev- 

 ery other inhabitable inland basin, we see reservoirs or evapora- 

 ting surfaces just sufficient for the supply of that degree of moist- 

 ure which is best adapted to the well-being of the plants and ani- 

 mals that people such basins. In other parts of the earth still, 

 we find places, as the Desert of Sahara, in which neither evapora- 

 tion nor precipitation takes place, and in which we find neither 

 plant nor animal to fit the land for man's use. 



803. Adaptations. — In contemplating the system of terres- 

 ABAPTATioNs-their trial adaptations, these researches teach one to re- 



beanties and sub- ^ ^ . , , , ^ 



limity. gard the mountam ranges and the great deserts oi 



the earth as the astronomer does the counterpoises to his tele- 

 scope — though they be mere dead weights, they are, nevertheless, 

 necessary to make the balance complete, the adjustment of his 

 machine perfect. These counterpoises give ease to the motions, 

 stability to the performance, and accuracy to the workings of the 

 instrument. They are " compensations J'' Whenever I turn to 

 contemplate the works of nature, I am struck with the admirable 

 system of compensation, with the beauty and nicety with which 

 every department is adjusted, adapted, and regulated according 

 to the others ; things and principles are meted out in directions 

 apparently the most opposite, but in proportions so exactly bal- 

 anced that results the most harmonious are produced. It is by 

 the action of opposite and compensating forces that the earth is 

 kept in its orbit, and the stars are held suspended in the azure 

 vault of heaven ; and these forces are so exquisitely adjusted, 

 that, at the end of a thousand years, the earth, the sun, and moon, 

 and every star in the firmament, is found to come and twinkle in 

 its proper place at the proper moment. Nav, philosophy teaches 



