550 ANNUAL REPORT OF THE Off. Doc. 



wet clay soil derived from the clay shale deposited on an impervious 

 rock bed. In some counties, the Lower Ilelderberg limestone forms 

 good soil of considerable extent, and is useful on the shale and clays, 

 especially so on clay bottoms on account of its mechanical effect in 

 granulating- the finely divided particles. 



Besides the use of lime to change clay soil to make it more friable, 

 lime may have a chemical effect, to free potash and phosphoric acid 

 from soil combinations and correct acidity. Sand and clay are the 

 principal constituents of all soils and, if in proper proportion, give 

 it texture, and when vegetable material is mixed with it forms mold. 



Mixing soils is quite practical, but with present conditions also un- 

 profitable, considering the value of good lands. An acre of soil to 

 a depth of nine inches weighs about two thousand tons, so It would 

 be necessary to move a thousand tons to spread four and a half inches 

 of either clay or sand for* mixing. At a very low calculation of 

 twenty-five cents a ton for handling it would cost |250.00 to pre- 

 pare an acre which is more tha ^. the average value of good Pennsyl- 

 vania soil. 



The soil samples presented here are only a few of the many existing 

 over much of the State. All soils are derived from two sources; 

 Igneous or Volcanic and Aqueous, deposited by water. From these 

 are derived the great variety, changed by the every active elements: 

 wind, rain, snow, heat and cold. 



The igneous being the first formed rocks over the surface of the 

 earth, all the others are necessarily derived from that source, through 

 disintegration and transportation bj^ water, ice, gravity and volcanic 

 activity. All elements from which soils are formed were once a 

 general mass of unorganized material. 



The various minerals are all derived from the oceans, excepting 

 coal and graphite which obtained their carbon from the atmosphere. 

 The substances useful in agriculture, aside from the rocks, are de- 

 posits like salt, potash, phosphates and lime which accumulated from 

 previous existing forms, and held in solution in water. 



The Dead Seea and Great Salt Lakes are examples of the con- 

 densation going on and the salt mines and brines from which salt 

 is condensed are evidences of rock fornmtions having been deposited 

 at later periods, which covered the saline deposits. The other ele- 

 ments useful in agriculture are derived from the same sources. 



All soils contain certain fixed substances in varying proportions 

 and are fertile so long as certain elementary substances exist in a 

 soluble form. Whenever the time arrives through continued crop- 

 ping that a soil is depleted of the soluble elements accumulated dur- 

 ing past periods regardless of its origin, it will no longer produce re- 

 munerative crops. 



Its restoration and maintenance then becomes a problem of eco- 

 nomics of vast importance. Some soils like those of igneous and 

 organic origin, possess inherent substances in larger quantity and a 

 more soluble form than most of the sedimentary of clay and sand. 



Numerous chemical analyses of soil from various sections prove 

 that the same formation differ widely. The igneous granites and 

 traps from Bucks, Montgomery, Lehigh and Philadelphia counties 

 have a large per cent, of potash and soda varying from four (4) to 

 thirteen (13) per cent. Lime, magnesia, iron, silica acid, alumina 



