1907 Remeivsl 341 



Upon this subject of irrigation two considerations force themselves 

 upon one. In the first place, while acknowledging the general truth that 

 fertilizing materials are carried off from the laud by drainage, we do not 

 know the actual amounts carried away in this manner from areas of these 

 different formations, and consequently we are in the dark as to the prac- 

 tical utility of irrigation in certain areas. Secondly, some degree of 

 doubt is entertained as to whether the adverse conditions engendered by 

 keeping the soil wet for a longer time, which it is presumed would 

 follow if irrigation was practised, would not more than counteract the 

 advantages derived by the soil from a return of the nutrient substances 

 carried away. 



The opinion of such a man as M. Risler, director of the Agricultural 

 College of Paris, on this subject is, however, of great weight. He sa)S, 

 " The distribution of waters, as that of mineral matters, depends upon 

 the geological constitution of a country. By regulating their flow 

 according to the needs of nourishment of agricultural produce, the 

 wealth of France could be doubled." 



The soils derived from the igneous rocks are then dealt with, basalt 

 being shown to give rise to soils of greater value than those derived from 

 granite. 



Chapter XL discusses glacial drifts and the such monuments of the Ice 

 Age as erratics. Smoothed and striated surfaces, boulder-clays, moraines, 

 and eskers are successively described. 



The chapter on peat is highly interesting. The cause of bog slides 

 seems to lie in the fact that the lower layers of turf — black or stone turf 

 — have a higher specific gravity, and the upper layers — yellow turf— 

 a lower specific gravity than water. Bogs are higher towards the centre in 

 the vicinity of springs, and this is due to the fact that Sphagnum grows 

 much faster here than in other places. It thus happens that when a 

 great quantity of rain has fallen these springs are more copiously sup- 

 plied, and a reservoir of water is held between the upper and lower 

 layers. The sides eventually give way and a mass of mud turf is urged 

 along at varying rate sometimes a distance of two or three miles. 



In treating of the reafforestation of certain areas there is an interesting 

 zoological reference to the Pine Weevil, which wrought such damage to 

 young pine and larch trees planted at Curraghmore in three successive 

 years. 



The chapter on recent life forms is particularly interesting, and allusion 

 is made to the somewhat conflicting views of geologists and zoologists 

 as to the necessity or otherwise of postulating a land connection ot 

 Ireland with the Continent in early Pleistocene times, in order to allow 

 the incoming of certain types ot our flora and fauna, some of which, from 

 their affinity to Spanish types, are termed Lusitaniau, while others 

 are characterised as having northern affinities. 



Section III. is devoted entirely to the consideration of the Drifts ot 

 Ireland and their relation to the soils of the four provinces. It contains 

 much valuable information, the result of many years of research in the 

 field. 



