THE BRITISH NATURALIST. 



5 



another line of weakness with a resistance inferior to that of the old line, 

 it naturally flows in this new direction ; nor does it signify at what angle 

 the new line lies, provided it is not in a higher plane than the old course. 

 Knowing these facts, then, we have but to scrutinize the course of the 

 dale in order to discover the different " joints " in the rock, which are to 

 be met within all stages of denudation, more or less prominent according to 

 the amount they have been " weathered," i.e., acted upon by the rain and 

 aqueous vapours, etc., contained in the atmosphere. Different rocks have 

 different ways of 44 weathering." A little reflection will enable us to 

 grasp the fact that things were not always as we find them now ; the 

 river and the valley must both have had a beginning. And so, Geology 

 tells us they have, a beginning so different from their present state, that, 

 until we thoroughly understand the explanation, we hardly like to credit 

 the facts. 



The whole of this deep valley was, at one time, nothing more nor less 

 than a subterranean watercourse flowing through a bed of carboniferous 

 limestone. But the waters of the stream, charged with the carbonic acid 

 gas which they had absorbed from the air or picked up from decaying 

 vegetable matter, dissolved, year by year, enormous quantities of the 

 limestone rock, carrying it in solution to the sea, where, after passing 

 through many strange changes, which we cannot for the present consider, 

 it was finally deposited as part and parcel of a submarine bed of 

 limestone or chalk, destined no doubt in the far distant future to appear 

 again as terra fir ma. 



In order to obtain some adequate idea of the enormous amount of 

 solid material which is transported in solution from the land to the sea by 

 rivers, we may quote that of the river Thames at Kingston, where no 

 less than 584,230 tons of mineral matter, chiefly carbonate of lime, flow 

 past every year. 



By the internal erosion of the river, combined with the external action 

 of the atmosphere, the roof of the watercourse is at length worn out, 

 falling down into the bed of the stream, where, offering a greater resist- 

 ance to the current, it soon becomes dissolved and washed away, leaving 

 the river free to continue the deepening and widening of its bed, greatly 

 aided by the action of the rains and winds, which can now act directly on 

 the surface of its banks. 



{To be continued.) 



In Burtonwood, near Warrington (January 27), the Sallow is in bud, 

 almost in flower. Hazel in full flower, male and female. This is very 

 early.— A. J. J. 



