348 G. H. Kinahan — On the Growth of Soil. 



similar increase in the depth of the main valley of the Wye so 

 altered the general drainage of the district, that water almost or 

 entirely ceased to flow along the old channel. The point of chief 

 interest is, therefore, this — that the facts lead us to believe that by 

 far the greater part of such a valley as Deep Dale has been excavated 

 since the surrounding country was dry land, probably chiefly by 

 means of the same slow process of erosion as is now taking place, 

 though the distribution of gravel brought from a distance indicates 

 that this part of England has been again below the level of the sea 

 at a comparatively recent period. 



IV. — Additional Notes on the G-kowth of Soil. 

 By Gr. H. Kinahan, M.E.I.A., etc. 



IN the former notes ^ "On the growth of soil," I omitted to speak of 

 the labours of the ants — these workers, although such pigmys in 

 this country, and, therefore, compared with the earth-worms, less capa- 

 ble, individually, of work, are so numerous and energetic, that in the 

 special places to which they resort, their yearly work is much more 

 conspicuous than the annual worm-work ; but the animals operate in 

 different places, for while the earth-worm luxuriates in rich highly- 

 cultivated land, the hill -building-ant loves a dry, sandy or peaty soil. 

 In the spring the ants may be observed beginning their work, and 

 from that time they carry on their operations all through the sum- 

 mer, to the late autumn, or early winter. On a moor they raise hil- 

 locks scattered promiscuously about over the ground, getting closer 

 and closer together as the colonies increase. But where the ants are 

 most useful is in places where crags and large stones are mixed up 

 with patches of sandy peat. In such a locality they will always 

 build on a rock, the foundation of their habitation being at its junc- 

 tion with the soil. These ants seldom raise their structures as high 

 as the moorland ants, but they make iip in extent for absence in 

 height, and hy this means the rocks are gradually covered with soil 

 and vegetation ; for, on account of the season of the year at which 

 they build, the growth of the plants keeps pace with the formation 

 of the ant-soil, and protects it in a great measure from " Meteoric 

 abrasion."^ During the winter, however, the shajDC of the ant-hills is 

 somewhat modified, but the matted roots of the plants preserve the 

 major part of the soil which will thus remain, forming an envelope 

 for the rock. 



As the annual work of one colony is rarely less than two square 

 feet in superficial area, and sometimes exceeds a square yard, the 

 yearly work done by a number of colonies must be very consider- 

 able. The ants that build in the sandy moors seem to frequent 



^ Geological Mag., June, 1869, page 260. 



"^ "When I proposed chemico-fluvial denudation as a better name than the vague 

 term suh-aerial denudation, I had quite forgotten that Mr. Scrope some time since, 

 called the same action Meteoric abrasion. — \_Geology and Extinct Volcanoes of Central 

 France.'] This name is evidently so much superior to any since proposed, that I am 

 surprised it has not been universally adopted. 



