SOILS AND THEIR COMPOSITION. 165 



Gravels and sands differ but little from each other except in fine- 

 ness^of the particles of which the}' are composed. But a sand or a 

 gravel may differ from another sand or gravel very much in its con- 

 stituent elements, owing to its being ground down from a different 

 kindjof rock. It may be said in general that gravels and sands 

 usually consist of the same element, principally silica. The}- differ 

 from each other in the particles of the sand being much smaller and 

 more uniforra^in size in sand than in the gravel. Gravel and sand 

 appear to have been produced by being ground down by natural 

 forces, while loams and clays are formed by chemical decomposition. 

 Where gravels consist mostly ot hard pebbles which decompose ver}' 

 slowlv itjis worthless for cultivation. But when the material is not 

 too hard and has a fair amount of clay and decayed vegetable mat- 

 ter, and a subsoil that will hold water, it will usually produce fair 

 crops. There is a kind of flat gravel, or slate, which is very poor 

 soil when coarse but decomposes rapidly, and when fined down forms 

 affair soil. There are spots in my fields where forty years ago the 

 plow would turn up slate as large as my hand and on which nothing 

 would fgrow that now is fine enough and fertile enough to produce 

 good crops, and it is an encouraging fact to farmers on slaty lands 

 and shoal soils lying on slaty rock, that the rock is rapidly decom- 

 posing and the soil growing deeper and finer. There are spots in 

 my fields that forty years ago were nearly bare rock that now have 

 sufficient soil to bear very good crops except in very dry seasons. 

 Sands are composed of finer particles than gravels, but are usually 

 from very hard rock and decompose slowly. Consequently they are 

 difficult to improve, and unless they contain a considerable portion 

 of clay and decomposed vegetable matter, so as to form loam, such 

 lands had better be allowed to grow wood. Gravels and sand have 

 some advantage over heavier and richer soils. The}' can be culti- 

 vated very early in spring, warm quickly by the sun, retain heat 

 well, and where one can afford to manure often such lands are good 

 for early maturing crops. But to the man about to purchase land 

 for general farming, I would say avoid gravels and sands. 



Loams are intermediate between gravel and clay, and are called 

 gravel-loams or clay-loams as they tend toward the one or the other 

 in composition. They differ from gravels in being finer and con- 

 taining more vegetable matter. They differ from clays in being less 

 compact and adhesive, and usually contain less potash and more 

 lime. Most of our light loams contain abundance of lime but are 



