ANNIVEESARY ADDRESS 0¥ THE PRESIDENT. Ixvii 



the Purbeck period, which caused the alternation of freshwater and 

 marine deposits on the flanks of the mountain-chain. And when, in 

 the Diluvial or Glacial epoch, the elevation had reached its maximum, 

 the height attained by the upper peaks and ridges was due, first, to 

 their having been formed of a quantity of material which has since 

 been worn away, and, secondly, to the whole range having been 

 bodily lifted upon a higher base or pedestal, from which position it 

 has again descended by gradual depression between the time of the 

 greatest extension of the glaciers and our own day. 



If we examine the mean height above the sea of the termination 

 of the glaciers of the Bernese mountains, it proves to be, for a mean 

 latitude of 46° 33', 4633 feet, and for those of the Savoy and Pen- 

 nine group, in mean lat. 45° 55', 4834 feet, giving a difference 

 which would amount to 317 feet for one degree of geographical posi- 

 tion. Calculating thence for a general mean north latitude of 

 46° 11' 3" a height of 4693 as the terminal height of the glaciers, 

 it ^vi]l be found coincident with a mean atmospheric temperature of 

 3°*7C. (38°-72 F.); and at a height corresponding with this tempe- 

 rature the ancient glaciers, whose relics are now found at much 

 lower levels, must also have come to their termination. 



Taking now for comparison the terminal moraines (Steinwalle 

 ifec.) which mark the former limits of the great glaciers of the 

 " diluvial " period on the north side of the Alps, we have, for a mean 

 latitude of 46° 55' 7", a height of 1416 feet above the sea, to compare 

 which with the present mean height of 4693 feet, we may reduce 

 both to the same position in latitude (that of Monthey), 46° 15', and 

 shaU then have the respective heights of 4673 (h) and 1202 (h') feet. 

 Assuming further, that the mean annual temperature in the so- 

 called Glacial period was higher than the present by 0°-19 C, by virtue 

 of the earth's internal heat, a further lowering of level by 90 feet 

 would have to be allowed for the terminus of the glaciers of those 

 times. 



"We should then, on this principle, require a depression of the 

 north side of the Alps, since the period of the great glaciers, of 



j(i_(;i'_90)==4673-1112=3561 feet*, 

 and by a similar inquiry, for the south side of the Alps, reduced to 

 the mean latitude of Ivrea, as the centre of these phenomena along 

 the southern flank of the chain, 



7i-;i'=4920-890 = 4030 feet;— 

 whence, with a limit of error of + 190 feet, it may be inferred that 

 the southern side of the great chain has been depressed about 500 

 feet more than the northern since the time of the great development 

 of ice and snow. 



* A very similar resiilt was indicated by Mr. David Milne Home, Edinb. 

 New Pliil. Jour., soon after von Waltersliausen's treatise was sent to the Haarlem 

 Society, viz. in 1861. Taking the average elevation of the melting point of Swiss 

 glaciers at 4400 feet, and the height of Geneva as 1335 feet, above the sea, Mr. 

 Home takes the difference, or 3065 feet, as the height to which that part of 

 Switzerland, would have to be raised to cause such a temperature as would en- 

 able the glaciers to reach Geneva without melting. 



