ESCHER ERRATICS OF SWITZERLAND. 13 



answered with certainty, although it is undeniable that certain con- 

 ditions appear to speak in favour of it in the Christiansand and 

 Arendal districts, as well as in many other tracts of Norway (Saters- 

 dalen, Hekkefiord, Krageroe, Modum, &c.). We may perhaps 

 accord a primordial character to one portion of the gneiss. 



With respect to the causes of the metamorphosis we have been 

 considering in the clay-slate and limestone, we may be certain 

 according to what we know of analogy, that at any rate heat has 

 formed one of these causes. That water also has taken part in 

 the operations is possible and indeed highly probable ; since strata 

 deposited in water would still be under aqueous conditions during 

 their transformation, and would be subjected to pressure from the 

 overlying mass of water. Scarcely, however, ought we to ascribe to 

 water so much power as to extinguish, as it were, the fire of the 

 Plutonists. Indeed the facts speak forcible against a Neptunism, 

 such as that in former times hastily sketched, and in later times 

 cleverly drawn, still scarcely true to nature. 



[T. R. J.] 



On the Drift Phenomena o/" Switzerland. 

 By A. EscHER VON der Linth. 



[Leonhard u. Bronn's N. Jahrb. f. Min. u. s. w. 1852, p. 726; and Heer and 

 Escher, two Memoirs (on the District of Zurich in the later Geological Periods). 

 Zurich, 1852, 4to, with plates.] 



The author gives the history of our knowledge of the erratic blocks, 

 sketches the outlines of the theories that have been founded on them, 

 describes the phenomena in Switzerland particularly, and lays down 

 on a map the distribution of the blocks in that region, with reference 

 to their respective local origins, their line of passage, and especially 

 the position of the long mounds of blocks or moraines, throughout 

 Switzerland and the neighboui'ing countries. Lastly, he offers a 

 clear explanation of the so-called Ice-period and its termination . He 

 has no doubt that the glaciers of Switzerland had really once the 

 enormous magnitude and extent which the moraines and erratic 

 blocks still indicate. A long series of rainy years at the present 

 time causes the glaciers to rapidly descend far down the valleys, if 

 there be no south wind [Fohn], which in a very short time can thaw 

 the greatest accumulation of ice and snow. Without this south wind 

 (and the Gulf-stream ! Ed. Jahrb.), Switzerland would have a climate 

 like that of the most southern part of America, the latitude of which 

 corresponds to that of Lugano and Tessin, and where the glaciers at 

 present come down to the sea*. This south wind, however, dates 



* Compare Hopkins, Quart. Journ. Geol. Soc. vol. viii. p. Ix. et neq., and p. 56 

 et seq. — [Ed. Jahrb.] 



