E. W. Hilgard—Flocculation of Particles, 211 
all sizes; colluvial rather than alluvial, and usually called 
“loams.” The i i 
several sediments and their combinations, still remain to be 
determined ; and the task is not a light one. 
t is known that the longer a soil has been maintained in 
perfect tilth, the more difficult it is to “puddle” it by wet 
plowing. Thisis doubtless owing to the gradual cementation 
of the floccules by the soil water; which fixes them, as it were, 
more or less permanently. 
As to the action of frost on soils, it is clear that as the 
water-menis¢ci within the floccules freeze, the soil must be re- 
_ duced to its ultimate mechanical elements, held apart by the 
 icecrystals. It is thus readily intelligible why plowing too wet, 
: 7 a freeze, is so much more injurious to tilth than when done 
after only a rain. But when the thawed soil is allowed first to 
assume its proper moisture-condition, the newly-formed floe- 
cules are of course looser than ever; and in clay and loam soils 
_ the most perfect tilth is the result, while clayless ones are 
measurably ‘ puddled” by fros 
reduce the kaolinite ingredient of soils and eg a ay ne 
oiling, I have 
formation, unless accompanied by mechanical agencies: we 
