JOHN P NORTON'S ADDRESS. 227 



posit of nearly a foot in depth was found, having quite a clayey- 

 character, baking hard, and cracking when dry. This deposit 

 has proved worth nearly or quite as much as manure on the 

 light sandy soils of that neighborhood. 



Soils, formed in this way by water, are common in every coun- 

 try, and there are also large tracts covered by some of those 

 terrible ancient floods of which I have spoken. This may all 

 have been done at the period of the deluge, but, however that 

 may be, the original formation is covered sometimes to a vast 

 depth by the debris of others. In all of these cases of superfi- 

 cial deposit, the character of the underlying rock has, of course, 

 little or nothing to do with that of the soil : but in most situa- 

 tions it has a controlling influence, and a study of the one will 

 give us a general idea of the other, beside leading to important 

 practical results. 



The variations in the composition of diflerent rocks are far 

 greater than is ordinarily supposed. It might be thought by 

 many for instance, that the soils of limestone countries would as 

 a general rule be nearly identical in composition, but this is by 

 no means true. The purer limestones contain as high as nine- 

 ty-five per cent, of carbonate of lime, but there are many which 

 contain impurities to the amount of much more than half their 

 weight. Then, too, there is a large class of limestones in which 

 magnesia is found in greater or less proportion. The soils pro- 

 duced by these last, when the magnesia is in large quantity, are 

 frequently very poor and cold ; differing extremely from those 

 formed by a limestone in which little or no magnesia is present. 

 An unpractised eye would be unable to distinguish between the 

 two kinds of stone, and a farmer, who had lived upon a good 

 limestone soil, might be miserably deceived when he thought he 

 had settled upon another of the same character. In the south 

 of England, on. the chalk formation, there are, among many 

 others, two layers of chalk, the one immediately above the 

 other, extending over a large district. The upper layer differs 

 little in appearance from the lower, except that it contains a 

 larger number of flints; but the soil produced by its decompo- 

 sition is thin and poor, while that from the lower is very fertile. 

 So marked is the diflerence, that this layer is carted as a ma- 



