﻿1850.] 



TRIMMER ON THE ERRATICS OF KENT. 



37 



the remains of the great extinct mammals ; and by combining and 

 exhibiting those phsenomena on maps. Maps of the surface-geology 

 will also be of great importance to agriculture. Professor Johnston 

 was the first to point out the necessity for them. " We have," he 

 says, in his Lectures, " geological maps of all our counties, in which 

 the boundaries of the several rocky formations are more or less ac- 

 curately pointed out ; and from these maps, as we have seen, much 

 valuable agricultural information may fairly be derived. We have 

 also agricultural maps compiled with less care and often with little 

 geological knowledge : but agriculture now requires geological maps 

 of her own, which shall exhibit, not only the limits of the 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 afford a sure basis on 

 which to rest our opinions in regard to the agricultural capabilities 

 of the several parts of a country, in which, though the rocks are the 

 same, the soils may be different. To the study of these drifted ma- 

 terials, in connexion with the action of ancient glaciers, the attention 

 of geologists is at present much directed, and from their labours agri- 

 culture will not fail to reap her share of practical benefit. The Geo- 

 logical Survey, so ably superintended by Sir H. de la Beche, is col- 

 lecting and recording much yaluable information in regard to the 

 agriculture of the Southern counties ; but it is not unworthy the con- 

 sideration of our leading Agricultural Associations, whether some 

 portion of their encouragement might not be beneficially directed 

 to the preparation of agricultural maps, which should represent by 

 different colours the agricultural capabilities of the different parts of 

 each county, based upon the knowledge of the soils and subsoils of 

 each parish or township, and of the rocks, whether near or remote, 

 from which they have been derived." 



It was by this hint that I was induced to enter on the task of 

 mapping the surface-geology of Norfolk, having been long satisfied, 

 from previous acquaintance with the superficial deposits, that their 

 influence on agricultural geology was greatly underrated. In the 

 progress of the work I soon discovered, that the variations of soils are 

 mainly dependent on contours ; — views which have received confir- 

 mation from a fact which has only recently come to my knowledge, 

 namely that this is a rediscovery. It had been asserted as a local 

 truth by an agricultural writer of considerable note*, before the rise 

 of geology and the construction of agricultural maps, and consequently 

 before the over-generalization which pushed the dependence of soils 

 on the strata exhibited in those maps, like the identification of strata 

 by organic remains, beyond its due limits. This map of the surface- 

 geology of Norfolk was, I believe, the first attempt to cor struct an 

 agricultural map on so large a scale as that of the Ordnance Map, and 

 with so much attention to details. The second was that of part of Car- 

 diganshire which I constructed for the Government Geological Survey. 

 But the first published illustration of the plan, is, as I have recently 

 been informed, that which Professor Johnston himself has appended 

 * Arthur Young. 



