AGRICUIiTURAL MAPS — ACCUMULATIONS OF PEAT. 275 



sure basis on which to rest our opinions in regard to the agricultural ca- 

 pabilities of the several parts of a county in which, though the rocks are 

 the same, the soils may^be very diflferent. To the study of these drifted 

 materials, in connection with the action of ancient glaciers (p. 269), the 

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

 agriculture will not fail to reap her share of practical benefit — the geolo- 

 gical survey, also, so ably superintended by Mr. De La Beche, is col- 

 lecting and recording much valuable information in regard to the agri- 

 cultural geology of the southern counties — but it is not unworthy the con- 

 sideration of our leading agricultural societies. — whether some portion of 

 their encouragement might not be beneficially directed to the preparation 

 of agricultural maps, which should represent, by different colours, the agri- 

 cultural capabilities of the several parts of each county, based upon a 

 knowledge of the soils and sub-soils of each parish or township, and of 

 the rocks, whether near or remote, from which they have been severally 

 derived. 



Before leaving this subject, I will call your attention to one practi- 

 cal application of this knowledge of the extensive prevalence of drifts, 

 which is not without its value. Being acquainted with the nature of the 

 rocks in a country, and with its physical geography — that is, which of 

 these rocks form the hills, and which the valleys or plains — we can pre- 

 dict, in general, that the materials of the hills will be strewed to a greater 

 or less distance over the lower grounds, and that these lower soils will 

 thus be more or less altered in their mineral character. And when the 

 debris of the hills is of a more fertile character than that of the rocks 

 which form the plains, that the soils will be materially improved by this 

 covering : — the soil of the mill-stone grit, for example, by the debris of 

 the mountain lime-stone, or of a decayed green-stone or a basalt. On 

 the other hand, where the higher rocks are more unfruitful, and the low 

 lands are covered with sterile drifted sands brought down from the more 

 elevated grounds — a knowledge of the nature of the subjacent rock may 

 at once suggest the means of ameliorating and improving the unpromis- 

 ing surface-drift. Thus the loose sand of Norfolk is fertilized by the 

 subjacent chalk marl; and even sterile heaths (Hounslow), on which 

 nothing grew before, have, by this means, been made to produce luxu- 

 riant crops of every kind of grain. 



§ 6, Of superficial accumulations of Peat. 



Of superficial accumulations, that of peat is one which, in the United 

 Kingdom, covers a very large area. In Ireland alone, the extent of bog 

 is estimated at 2,800,000 acres. None of the drifted materials we have con- 

 sidered, therefore, would appear so likely to falsify the predictions of the 

 geologist, who should judge of the soils of such a country from informa- 

 tion in regard to the rocks alone on which they rest — from a geological 

 map for example — as the occurrence of these peat bogs. Yet there are 

 certain facts connected with the formation of peat, which place him in 

 some measure on his guard in reference even to accumulations of vege- 

 table matter such as these. 



1°. There is a certain range of temperature within which alone peal 

 seems capable of being produced. Thus, at the level of the sea, it is 

 wove.r f()und nearer the equator then between the 40° and 45° of latitude; 



