158 Reviews. [Jan., 



lands are cleared, and converted into fields and pastures, the gain to 

 mankind is not so great as it might at first appear. 



Among the uses of forests Mr. Marsh includes that of holding up 

 the rocks in mountain districts, and preventing avalanches. That in 

 certain cases they may have done this there is little doubt, although, 

 of course, a forest would not check the descent of an avalanche once 

 in motion. 



It is not only for the sake of the timber, or for clearing land for 

 other crops, that forests have been removed. In settled countries 

 they are often cut down for some peculiar or local reason. As retreats 

 of criminals, or as harbouring birds which are believed to steal fruit 

 and grain, trees have been removed in large quantities. In Spain, a 

 country where the effect of wood would be eminently favourable, the 

 superstitions of the people absolutely prevent planting with any 

 chance of success. 



As, then, the destruction of forests by man has often had a great 

 and injurious effect on climate — rendering it more extreme, and dimi- 

 nishing the quantity of land covered by vegetation — increasing the 

 torrents in mountain districts, lowering and making irregular the 

 height of water in streams, and reducing the springs over large dis- 

 tricts — it behoves men associated under governments to keep apart a 

 certain definite proportion of their lands for forest cultivation, and 

 thus bring back a more favourable condition for the cultivation of the 

 rest of the country. 



The effects of human labour in reclaiming from the sea lands 

 already covered with water, and still more in preventing those occa- 

 sional incursions on border-lands which render them useless and 

 mischievous, are too well known to need remark. Thus, on the east 

 coast of England, half a million of acres of unhealthy marsh, pool, 

 and tide-washed flat, have been converted into healthy arable land and 

 pasture. 



Large as this result may seem, it is little more than half that 

 which has been recovered on the opposite shores of Holland. The 

 works by which these great results are obtained, are exceedingly 

 costly, and require incessant and most careful supervision. They are 

 human in their origin, and if left alone for a few years, they would 

 not fail to be destroyed by the constant encroachment of the sea. 

 Whenever, also, the soil is less than four or five feet above low- 

 water level, pumps worked by wind, water, or steam, must be employed 

 to keep the land dry enough for use. There can be no doubt that 

 human influence, by extending the area of low lands near the sea, and 

 at the same time removing a large quantity of surface-water, has 

 affected the climate in the districts where this work has been carried 

 on on a large scale ; but a still greater effect has been produced by 

 the lowering of lakes — an operation largely executed not only in 

 Europe but in the East. Such works, by reducing the water-surface 

 of a country, diminish the evaporation, and also the supply to be 

 obtained from springs and rivulets at low levels. Ordinary draining 

 operations carried on largely in cultivated lands, cannot but produce 

 a large result, which is, on the other hand, counterbalanced by the 



