148 



DIFFERENCE OF SOILS. 



with a microscope, will be found to consist of the 

 same ingredients, containing, perhaps, minute specks 

 of the brown oxide of iron, derived from the pyrites 

 or protoxide of iron usually contained in that rock. 

 Where gneiss is the prevailing rock, the soil will be 

 composed of the same materials, only the mica is 

 more abundant. In a mica slate region, we have a 

 soil consisting chiefly of mica^ mixed with grains of 

 quartz. Syenite 2i,wd hornblende rock produce a dark- 

 coloured soil, containing much feldspar and decom- 

 posed hornblende, with but little quartz. The soil 

 in the neighbourhood of greenstone trap rocks has a 

 dark brown colour, containing pieces of the unde- 

 composed rock, and is of a soft, loamy character, 

 and exceedingly fertile. Where slate rocks prevail, 

 the soil is of a blue colour, and forms a deposite of 

 tough blue clay when transported by water. In 

 limestone countries we can easily perceive that the 

 soil is made up of the ingredients of this mineral; 

 its colour, of course, depending on the colour of the 

 rock, and the quantity of vegetable matter contained 

 in it. Some of the magnesian limestones, or dolo- 

 mite, decompose very rapidly when exposed to the 

 atmosphere; and we have seen such in Litchfield 

 " county. Conn., forming, from their disintegration, 

 large beds* of a coarse white sand. 



* * It is a somewhat remarkable fact, ascertained by Prof. Hitch- 

 cock, that it is a rare thing to find in the soil of a limestone country 

 any calcareous matter. Restates that out of 125 specimens of 

 soils from all parts of the State of Massachusetts, and several of 

 them from limestone tracts, only seven exhibited any eiferves- 

 cence with acids, and 3 per cent, was the greatest quantity of 

 lime contained in any of them. From numerous experiments, 

 he concludes that only one in 30 of the soils of Massachusetts 

 contains calcareous matter. Quere : What becomes of it? If 

 lime is a simple substance whose base is calcium (a metal), it is 

 very difficult to believe that calcareous matter " is consumed or 

 changed," as Prof H. states to be a fact. Does this fact not 

 lend great probability to the supposition that calcium is a gaseous 

 compound, and may thus be produced by the secretory organs of 

 animals? 



