Mr. Harkness 0/2 Changes in the Temperature of the Earth. 145 



The consequence of supposing numerous icebergs to have floated, 

 at a former period, into latitudes in which icebergs are never seen at 

 present, is, that the temperature of these regions and of the whole 

 earth at that period was lower than it is at present ; and the less 

 the distance to which the icebergs were floated from the glacier they 

 were originally launched from, the further must the then frigid have 

 encroached on the now temperate zone. 



The erratic blocks which are found at various elevations on the 

 declivities of the Alps, and which sometimes form large mounds 

 placed transversely to those declivities, resemble in that respect the 

 morains formed by glaciers ; and hence it has been inferred that it 

 is by the action of glaciers that these alpine boulders have been 

 transferred to their present sites. Supposing that to have been the 

 case, the ancient glaciers must have extended to a much lower level 

 than the modern glaciers ; and the temperature of the Swiss valleys 

 must have been lower than it is at present. The glacier theory 

 therefore leads to the conclusion, that when these ancient morains 

 were formed there existed a frigid climate in the now temperate 

 zone. 



There have been observed in many and very remote parts of the 

 world, at considerable elevations above the present sea-level, ex- 

 tending through great distances of country, long terraces of trans- 

 ported materials, such as sand, clay, and pebbles ; and these ten-aces 

 geologists have agreed in considering as the remains of ancient sea- 

 beaches. These beaches sometimes contain sea-shells, which belong 

 partly to arctic species. 



In the great majority of instances these terraces are horizontal ; 

 and when that is the case, and more than one of these terraces form 

 continuous lines in the same district, they are all of course parallel 

 to one another. Brongniart, in the year 1829, was the first to call 

 attention to terraces of this description, the origin of which he attri- 

 buted to the subsidence of the waters of the ocean. This supposition 

 has by some geologists been considered as at variance with physical 

 probabilities ; and the more generally received hypothesis now is, 

 that these terraces owe their present position to elevation by subter- 

 ranean agency. 



This explanation at first sight appears very probable; and the 

 more so as there are some ancient beaches which are not horizontal 

 but are inclined to the horizon. Of this description are the two 

 observed in Norway, between the 70th and 71st degrees of north 

 latitude, by Mons. Bravais ; of which the upper descends from its 

 summit level of 222 feet above the sea to its lowest level of .94 feet ; 

 and the lower descends from its summit level of 91 feet to its lowest 

 level of 46 feet. The present position of these Norwegian beaches is 

 probably owing to the same cause which has raised, and still con- 

 tinues to raise, a part of the Scandinavian peninsula above the level 

 of the ocean, and which has given rise to the ancient sea-beaches in 

 Sweden. It appears, how r ever, from the discovery of a human ha- 

 bitation in connexion with these beaches in Sweden, that they be- 

 long, not to the post-tertiary, but to the historical epoch ; and it is 



Phil. Mag. S. 3, Vol. 24. No. 157. Feb. 1844. L 



