Notices of Memoirs — The Terraces of Norway. 75 



Since 1858, when lie began a series of observations on tbese 

 terraces, Prof. Kjerulf has pointed out three causes to which these 

 terraces may have been due. 



1. The former position of the sea, which left its highest marks on 

 the land at 600 feet above the present level. 2. Ancient bottom 

 moraines, which obstructed the valley at a time subsequent to the 

 Glacial period, creating dams, so that a basin could be formed in the 

 water-course. 3. Obstruction by a mountain which might create a 

 basin so long as the water-course in the valley did not erode still 

 deeper into the dam. 



In his opinion the ultimate causes of the steps of the water-courses 

 are not different, but there was one main cause, namely, the presence 

 of a water surface, which caused the materials washed down by the 

 streams to be heaped up everywhere to the height marked out. 



Where the watercourse joined the sea without any obstruction, the 

 materials brought down through the valley might be piled to a con- 

 siderable height at this level and below it. Where, however, a bottom 

 moraine obstructs the passage, a basin may be formed inside this 

 wall, and the material of the water-courses piled as high as the sill. 

 A similar case is the obstruction caused by the spur of a mountain. 

 Then supposing the sea-level to be lowered, the dam broken through, 

 or the mountain obstruction opened, at each of those spots some 

 portion of the piled-up materials will remain at the sides of the 

 passage, subsequently to be dug out by the water, or else the 

 terraces will show the former water-level. 



The steps of the water- courses are directly connected with the 

 question of upheaval, and the author confidently adheres to the 

 belief that the land has only risen 600 feet since the Glacial epoch. 

 Lyell's theory of a sinking and rising of 6,000 feet is shown to be 

 unsupported by facts ; and in regard to the question of time, that 

 whereas this theory would require a period of 480,000 years, it is 

 hereby reduced to 24,000. 



The terraces or water-courses throw Kght upon the uniformity of 

 rate of the motion of the land. 



The terraces above the highest beach-mark can almost always be 

 attributed to dams and other obstructions. The case is, however, 

 different as regards terraces lying below this mark ; for these lie 

 entirely open to the mouth of the valley, and they are unsupported 

 by dam or obstruction of any kind. 



The formation of the terraces has been generally attributed entirely 

 to the sea. But, Prof. Kjerulf remarks, the sea alone could never 

 form a terrace, as may be plainly seen by any one sailing round the 

 coast of Norway, for he will observe that the shores are not sur- 

 rounded by terraces, but that they occur in few places only — in 

 those, namely, where a water-course opens out. The chief work of 

 these latter consists in transporting gravel and mud down to the 

 nearest water-basia. The terrace is formed by the joint labour of 

 the stream and the sea. Now if the sea sank equally and slowly, 

 there is no cause at hand for the formation of high, distinct, regular, 

 and open terraces, one below another. On the contrary, for the 



