PRACTICAL AGRICULTURE. 197 



made up of one or many soils. If one kind prevailed 

 through the whole, it might be worth while to procure 

 an analysis, as in that case a single analysis would ap- 

 ply to the whole farm ; whereas, if there were various 

 kinds of land, several analyses would be required, and 

 the expense would be greater. 



372. If all the varieties of soil were found on this 

 farm, we should have, according to a classification, re- 

 commended by Professor Johnstone, and now pretty 

 generally adopted : — 



1. Pure clay, from which no sand, or not more than 5 



per cent, can be washed ; containing about 60 per 

 cent, of silica, combined with about 40 of alumi- 

 na, as silicate of alumina. 



2. Strong clay soil, suitable for brick, containing from 



6 to 20 per cent, of silicious sand. 



3. Clay loam, having from 20 to 40 per cent, of fine 



sand. 



4. Loam, containing from 40 to 70 per cent, of sand. 



5. Sandy loam, having from 70 to 90 per cent, of sand. 



6. Sandy soil, having upwards of 90 per cent, of sand. 



7. Peat, black vegetable matter, similar to swamp 



muck, except that it is filled with partly decayed 

 roots and stems of plants. 



8. Swamp muck, black, fine, similar to the last, but 



containing less, of partially decayed matter. 



373. Soils may be distinguished according to this 

 classification in the following manner : — Take 100 grains 

 of soil, dried on white paper, at a temperature as high 



