688 THE POPULAR SCIENCE MONTHLY. 



range for a distance of one hundred miles, and np to a height of 

 two thousand and fifteen feet above the Lake of Neufchatel. The 

 first important point to notice is that this highest elevation is 

 attained at a spot exactly opposite, and in the same direction as, 

 the Rhone Valley, between Martigny and the head of the Lake of 

 Geneva, while north or south of this point they gradually decline 

 in elevation to about five hundred feet above the lake. The blocks 

 at the highest elevation and central point can be traced to the 

 eastern shoulder of Mont Blanc. All those to the southwest come 

 from the left-hand side of the lower Rhone Valley, while those to 

 the northeast are all from the left side of the upper Rhone Valley 

 and its tributaries. Other rocks coming from the right-hand 

 side of the upper Rhone Valley are found on the right hand or 

 Bernese side of the great valley between the Jura and the Bernese 

 Alps.* 



Now, this peculiar and definite distribution, which has been 

 worked out with the greatest care by numerous Swiss geologists, 

 is a necessary consequence of well-known laws of glacier motion. 

 The debris from the two sides of the main valley form lateral 

 moraines which, however much the glacier may afterward be 

 contracted or spread out, keep their relative position unchanged. 

 Each important tributary glacier brings in other lateral moraines, 

 and thus when the combined glacier ultimately spreads out in a 

 great lowland valley the several moraines will also spread out, 

 while keeping their relative position, and never crossing over to 

 mingle with each other. So soon as this definite position of the 

 erratics was worked out it became evident that the first explana- 

 tion of a great submergence during which the lower Swiss 

 valleys were arms of the sea and the Rhone glacier broke ofi^ in 

 icebergs which carried the erratics across to the Jura was alto- 

 gether untenable, and that the original explanation of Venetz 

 and Charpentier was the true one. Sir Charles Lyell, who had 

 first adopted the iceberg theory, gave it up on examining the 

 country in 1857 and ascertaining that the facts were correctly 

 stated by the Swiss geologists ; and there is at the present day 

 no writer of the least importance who denies this. Sir Henry 

 Howorth, who is one of the strongest opponents of what he con- 

 siders the extreme views of modern glacialists, gives a full sum- 

 mary of the facts as to the old Rhone glacier from Charpentier. 

 He states that between Martigny and St. Maurice the moraine 

 debris on each side of the valley shows the glacier to have reached 

 a height of three thousand feet above the river ; farther on, 

 where the valley widens over the Lake of Geneva, it sank to 



*A map showing the lines of dispersal of these erratics is given in Lyell's Antiquity of 

 Man, p. :i44, and is reproduced in my Island Life, p. 111. 



