310 



PAN 



PAN 



is thawed. The frost does more 

 than tillage, and perhaps rnoie than 

 rains, or fermentation, towards 

 causing the more ponderous parts 

 of the soil (or ponderous bodies 

 in thi' soil) to subside, or sink. 



The frost may have another in- 

 fluence in increasing the compact- 

 ness of the under stratum. As 

 the frost expands the soil, the pres- 

 sure of it downward is increased ; 

 by which pressure, the matter of 

 which the pan consists, is made 

 most close and hard, like earth 

 thai hss been violently rammed. 

 Bui tbii perhaps can take place, 

 only when the frozen stratum is 

 heid down by strong objects, which 

 reach far below the frost and pan ; 

 as the stumps of large trees deeply 

 rooted, large rocks, &;c. 



Bui it will be objected, that 

 some soils appear to have no pan 

 under them. To answer this, it 

 may be said, that perhaps some 

 soils were originally made up of 

 particles equally ponderous ; so 

 that one had no more tendency to 

 subside than another. Or else the 

 looseness and openness of the 

 under earth in such places, was so 

 great that it could not stop the 

 ponderous parts of the soil in their 

 descent ; so that they have been 

 dispersed among the loose earth, 

 and part of them gone to a very 

 great depth. 



If I have given a just account of 

 the formation of the pan, will it 

 not follow, that this under stratum ' 

 is less penetrable in cold than in 

 warm latitudes, when made of like 

 materials ? So far as my obterva- 

 tion has extended, this appeal's to 



be the case. It ought also to be 

 lower in the earth, and the soil 

 deeper ; and future observations 

 may convince us that this also is 

 fact. 



Another corollary may be, that 

 deeper ploughing than is usually 

 practised in this country would be 

 proper. For it seems that nature 

 designed all the strata above the 

 pan to serve for pasture of plants. 

 And it is well known that the more 

 it is stirred and mixed, the titter it 

 is for this purpose ; not only be- 

 cause it lies the more loose and 

 open, but because the more of the 

 food of plants will be contained in 

 it. 



Such a stratum, at a right dis- 

 tance from the surface, is a great 

 benefit to the soil. For, as no ma- 

 nures can easily penetrate it, they 

 must remain in a good situation to 

 be taken up by the roots of vege- 

 ables. But where there is no 

 compact under stratum, unless at 

 a great depth, manures laid upon 

 the soil are partly lost. Hence 

 appears the great propriety of 

 claying and marling such soils. In 

 a long course of tillage, these 

 dressings will subside, and do 

 something towards forming the 

 stratum that is wanted. 



But to form a good under stra- 

 tum at o'nce, where it is wanted, 

 let one hundred or more loads of 

 clay be spread on an acre of sandy 

 grass land. After it has lain, 

 spread upon the surface one win- 

 ter, let it be made perfectly fine 

 and even by a bush harrow, and 

 rolled. Afterwards turn it under 

 with a very deep ploughing. This 



