180 On the Physical Properties of Soil 



make this determination as well with soil fully dried at 144^° F.^ 

 as also with soil thoroughly moistened ; we may consider a soil 

 thoroughly moistened when it is laid in a wet state on a filter, and 

 no longer allows any water to drop through. 



Several of the previously mentioned earths exhibited the fol- 

 lowing dift'erences in my experiments in reference to this point : — 



Kinds of Eavtli, 



Specific 

 Gravity, 

 that of 

 Water being 

 taken as=l. 



Wei<,'lit of a 

 Cubic Incli. 



Weight of a Cubic Foot 



In the 

 Dry state. 



In the 

 Wetstate. 



In the 

 Dry state. 



In the 

 Wet state. 







Grains. 



Grains. 



Pounds. 



Pounds. 





2.722 



505 



628 



113.6 



141.3 





2.653 



495 



605 



111.3 



136.1 





2.331 



408 



573 



91.9 



127.6 





2.601 



433 



577 



97.8 



129.7 





2.581 



393 



551 



88.5 



124.1 



StifF Clay, or Brick-Earth . 



2.560 



357 



531 



80.3 



119.6 





2.533 



334 



515 



75.2 



115.8 



Fine white clay (pipe clay) , 



2.440 



213 



454 



47.9 



102.1 



Fine Carbonate of Lime » . 



2.468 



244 



460 



53.7 



103.5 



Fine Carbonate of Magnesia 



2.194 



75 



339 



15.8 



76.3 





1.370 



154 



346 



34.8 



81.7 





2.332 



364 



457 



68.7 



102.7 





2.401 



376 



529 



84.5 



119.1 





2.631 



498 



624 



112.0 



140.3 



From this Table we derive the following general results : — 



1. Sand, either in its dry or wet state, is the heaviest part of 

 arable soil, certain fine slaty marls approaching the nearest to 

 sand in this respect. 



2. Calcareous and siliceous sand differ but little in this point of 

 view, calcareous sand, however, being the heaviest of the common 

 constituents of arable soil. 



3. The clays are lighter the more clay and the less sand they 

 contain, and the contrary. 



4. The lime always exhibits a great difference in weight, ac- 

 cording to the fineness of its particles and the mode of its prepa- 

 ration; that obtained from slaked lime has a remarkably less 

 weight, even when it has become again saturated with carbonic 

 acid, the reason of which seems to be the great expansion of 

 quicklime on its combination with water. That employed in this 

 experiment lay for six years spread out flat in the state of a fine 

 powder and exposed to the air. When lime is in close combi- 

 nation with carbonate of magnesia, as is the case in dolomite sand, 

 the compound of these two earths exhibits a much greater weight 

 than either of them in its separate state ; the specific gravity of 

 such kind of sand rises to 2.82 and 2.83, and even magnesian stony 

 marls often possess this greater weight. 



5. The carbonates of magnesia, as artificially obtained by pre- 

 cipitation from their solutions^ exhibit indeed the least absolute 



