THE ORIGIN OF SOILS 193 



the coarser particles being carried only by the swifter streams and 

 dropped as soon as the velocity falls, it is probable that it will 

 not resemble the soil we have already examined on the flanks of 

 the valley, a soil which had grown out of the rock beneath it. 

 There is bed rock beneath the river meadow soil if we cut down 

 deep enough, but when we do find the point of junction the change 

 from the rock to soil is clear and sharp, for the river silt has been 

 deposited on a clean rock surface, usually of an entirely different 

 character. We are now dealing with one of the cases alluded 

 to before, where the soil has not grown out of the rock beneath it, 

 but has been carried from a distance and deposited by water or 

 some kindred agency, giving rise to a " soil of transport " or 

 " drift soil," as it is termed, to distinguish it from the " seden- 

 tary " soil which has been formed where it lies. A soil of trans- 

 port may be similar to the rock below it if it happens to have 

 been originally derived from another area of similar rock, or it 

 may be entirely different as a rule the change from rock into 

 soil is sharp and distinct. A soil of transport is usually further 

 distinguishable by its uniform character ; as one descends there 

 is no increase in the number of the larger fragments of rock, 

 etc., which characterise the lower depths of a sedentary soil. 

 River meadow soils, indeed, are much of a type all over the 

 country ; they are a little lighter or a little heavier according 

 to the nature of the rocks in the river basin, and they vary 

 in their behaviour towards crops with the depth of the water 

 and the existence or not of a bed of gravel below the surface ; 

 they are classed generally as alluvial soils. On the flanks of the 

 valley, above the present alluvial level, areas more or less extensive 

 are often seen, covered with sand or gravel or brick earth, which 

 have obviously been originally water-borne into their present posi- 

 tion; these are the remains of old alluvial deposits which formerly 

 filled the valleys, but have been very largely removed through 

 certain geographical or climatic changes that have altered the 

 rainfall and so caused a newer valley to be carved out of the old 

 alluvian. Again, over great parts of the north and midlands of 

 England the surface of the country is covered with deposits, often 

 of great thickness, which have been transported by moving ice 

 during the last glacial epoch ; it depends rather upon the thickness 



VOL. V. 13 



