CLIMATE. 11 



is required annually for the production of timber on a fully- 

 stocked area. Amongst the substances thus brought to the 

 ground are calcium carbonate, magnesium carbonate, sodium 

 chloride, calcium sulithate, ferric oxide, alumina, silica, 

 organic nitrogenous matter, etc. Direct analysis has shown 

 that upwards of 800 lb. of these substances have been 

 deposited on an acre of land in one year, a quantity more 

 than sufficient to provide for that contained in a heavy 

 increment of wood laid on during the same period. In other 

 cases, observations have shown that the quantities deposited 

 are considerably less than 300 lb. per acre. 



5. Ammonia and Nitric Acid. 



Limited amounts of these important substances are con- 

 tained in the atmosphere ; they supply nitrogen to forest plants 

 in considerable quantities, especially for the formation of seeds. 



A certain quantity of ammonia and nitric acid is brought 

 into the soil by the annual rainfall ; where the latter is 

 heavy, the quantity of the above substances thus obtained by 

 the soil may be sufficient for all the requirements of forest 

 growth, but where it is light, this will not be the case. 



As already stated, certain plants (Leguminosse) can take 

 nitrogen direct from the air by means of tubercles or nodules, 

 which are produced by microscopic fungi or bacteria. Again, 

 further investigation may show that mycorhiza, a coat formed 

 by a fungus outside or inside the root, is connected with the 

 assimilation of nitrogen by the plant. 



Section II. — Climate. 



By climate is understood the local peculiarities of the 

 atmosphere in respect of temperature, degree of clearness, 

 moisture and rest or motion. As already indicated, the climate 

 of a locality depends on its situation. 



The climate of a locality is of greater influence upon the life 



