274 GENERAL DEDUCTIONS OF GEOJ.OGY STILL TRUE. 



characters and distinctions of the soil peculiar to each rock being stil 

 preserved beyond the spaces upon which they have been accidentally 

 intermingled. 



4°. To this, and to each of the other statements above njade, there are 

 many local exceptions. For instance, what is true of sands and gravels, 

 will not so well apply to the fine mud of which many clays are formed. 

 Once commit these to the water, and if it has any motion, they may be 

 transported to very great distances from their orii^inal site. Rivers, 

 lakes, and seas, are the agents by which these extensive ditfusions are 

 effected. The former produce what are called alluvial formations or de- 

 j)osits ; which are generally rich in all the inorganic substances that 

 plants require, and hence yield rich returns to the agricultural labourer. 

 They are usually, however, distinguished, and their boundaries marked, 

 by the geologist — so that the soils which repose upon them do not con- 

 tradict any of the general deductions he is prepared to draw, in regard to 

 the general agricultural capabilities of a country, from the kind of rocks 

 of which it consists. 



Thus though the occurrence of^xtensive fields of drift over various 

 parts of almost every country, does throw some further diflSculty over 

 the researches of the agricultural geologist, and requires from him the 

 application of greater skill and caution before he pronounce with cer- 

 tainty in regard to the agricultural capabilties of any spot before he visit 

 it— yet it neither contradicts the general deductions of the geologist nor 

 the special conclusions he would be entitled to draw in regard to the 

 ability of any country, when rightly cultivated, to maintain in comfort 

 a more or less numerous population. The political economist may still, 

 by a survey of the geological map of a country, pronounce with some 

 confidence to what degree the agricultural riches of that country might 

 by industry and skill be brought — and which districts of an entire conti- 

 nent are fitted by nature to maintain the most abundant population. 

 The intending emigrant may still, by the same means, say in what new 

 land he is most likely to find a propitious soil on which to expend his 

 labour — or such jnineral resources as will best aid his agricultural pur- 

 suits ; — while a careful study of the geological map of his own cotmtry 

 will still enable the skilful and adventurous /armer to determine in what 

 counties he will meet with soils that are suited to that kind of practice 

 with which he is most familiar— or which are likely best to reward 

 him for the application of the newest and most approved methods of 

 culture. 



Still there are some aids to this kind of knowledge yet wanting. We 

 have geological maps of all our counties, in which the boundaries of the 

 several rocky formations are more or less accurately pointed out, and 

 from these maps, as we have seen, much valuable agricultural informa- 

 tion may be fairly deduced. "We have also agricultural maps of many 

 counties, compiled with less care, and often with the aid of little geolo- 

 gical kpDwledge, as that of Durham in Bailey's ' View of the Agricul- 

 ture of ;he County of Durham,' published in 1810. But agriculture 

 now requires geological maps of her own — which shall exhibit not only 

 the limits of rocky formations, but also the nature and relative extent 

 of the superficial deposits (drifts), on which the soils so often rest, and 

 from which they are not unfrequently formed. These would atTord a 



