No. 129.J 317 



that most necessary of all the elements of plants, will be supplied 

 by the atmosphere by the accidental presence, if it is so pleased 

 to be expressed, of phosphoretted hydrogen j but it is from the 

 decomposition of the rooky particles of the soil that by far the 

 greatest supply of the mineral elements of plants is to be obtain- 

 ed. Thus, if we take the native rocks, even of the deepest lying 

 iharacter^ the granite, we shall J5nd that it is only necessary to 

 allow these to disintegrate, and we shall have some very impor- 

 tant food for plants provided. It contains 



Silica, 74.00 



Peroxide of iron, , 3 . 00 



Alumina, (clay) 12.20 



Lime, , .22 



Magnesia, .,.......,., . 46 



Potash and soda, , 9 . 33 



Fluoric acid and water, , . . . . . 50 



Here are at once the very elements of success in plant growing, 

 potash, soda, lime and magnesia, and the first named in as large 

 a proportion as nearly ten per cent. 



If again we take the basalt, we have these constituents: 



Silica, 53.70 



Alumina, . ..,.,..,.,...., 25 .41 



Lime, 4.55 



Magnesia, ....<..,=......,.,...,,.. 1 . 37 



Oxide of iron, ..,...,, «,...... 8.95 



Sulphuret " , traces. 



Water,.. ,,,....,,.... 4.30 



If we take sandstone, again we have 



Silica, . , ... . .... 54 .34 



Peroxide of iron, . . , , . 3 , 90 



Alumina, , 4.35 



Carbonate of lime, ....,..., 30 . 00 



Carbonate magnesia, 2.49 



Phosphate of iron, ,,, , 20 



Alkalies, traces. 



Water and loss,.*?.'.'.';':.''.^ .V .'-^.'Vv: ; 4 .72 



