360 MAN AND THE GLACIAL PERIOD. 



stream, which is usually insignificant, was so swollen by a 

 rainfall of a single day that it rose high enough to sweep 

 away an iron bridge the bottoms of whose girders were 

 sixty-five feet above high-water mark. One iron girder 

 weighing eighty tons was carried two miles down the 

 river, and nearly buried in sand. The significance of 

 these facts is enhanced by observing also that for fifteen 

 miles above the bridge the fall of the river only averaged 

 ten feet per mile. Floods to this extent are not uncom- 

 mon in India. During the Glacial period spring freshets, 

 must have been greatly increased by the melting of a large 

 amount of snow and ice which had accumulated during 

 the winter, and also by the formation of ice-gorges near 

 the mouths of many of the streams. It is probable, also, 

 that the accumulation of ice across the northern part of 

 the German Ocean may have permanently flooded the 

 streams entering that body of water ; for it is by no means 

 improbable that there was a land connection between 

 England and France across the Straits of Dover until 

 after the climax of the Glacial period. In support of his 

 theory, Mr. Tylor points to the fact " that the gravel in 

 the valley of the Somme at Amiens is partly derived from 

 debris brought down by the river Somme and by the two 

 rivers the Celle and the Arve, and partly consists of ma- 

 terial from the adjoining higher grounds washed in by 

 land floods," and that the "Quaternary gravels of the 

 Somme are not separated into two divisions by an escarp- 

 ment of chalk parallel to the river," but " thin out gradu- 

 ally as they slope from the high land down to the Somme." 

 Mr. Tylor's reasoning seems especially cogent to one 

 who stands on the ground where he can observe the size 

 of the valley and the diminutive proportions of the present 

 stream. Even if we do not grant all that is claimed by 

 Mr. Tylor, it is difficult to resist the main force of his 

 argument, and to avoid the conclusion that the valley of 

 the Somme is largely the work of preglacial erosion, and 



