——=—IEI=— i. ae 
‘ 
Prof. Struder on Bowlders. 325 
Arr. V.— Translations relative to Bowlders and Cobalt Ores, 
Jrom the Néues Jahrbuch fir Mineralogie, Geognosie, Geolo- 
gie und Petrefaktenkunde, herausgegeben von Dr. LeonaarDd 
und Dr. Brown. Jahrgang, 1838. Rev. W. A. Larnep. 
1. On the Recent Explanations of the Phenomenon of Erratic 
Blocks ; by Hr. Prof. B. Srruper. 
Tue wish expressed in your last letter of publishing in the 
Jahrbuch, my geological remarks upon the recent explanation of 
the phenomenon of erratic blocks, is the occasion of the following 
communication. 
After all the endeavors, observations, and speculations of the 
last ten years, we see the phenomenon of erratic blocks still veiled 
in a mist, which hinders us from taking a full and exact view of 
them, and which has not as yet permitted a general elucidation. 
Hence we are disposed to view every new theory with favor, and 
Wwe overlook at first its difficult points, though they may be not a 
few, because of the satisfactory explanation of others, on which 
we have hitherto labored in vain. : 
The floating or forcing of bowlders by powerful currents of 
Water, still appears to me, to afford the explanation, which best 
agrees with the facts, although at the same time I confess that I 
am not prepared with an entirely satisfactory answer to several 
admitted and recent objections. In order to hold up the blocks 
while floating from the Alps to the Jura, we suppose instead of 
streams of pure water, streams of mud and detritus, without being 
able fully to show what became of this smaller rubbish. In order 
to carry them over the deep Swiss lakes or the Baltic Sea, we 
assume a kind of lateral impulse, while we make the avulsion of 
the blocks cotemporaneous with the rise of the mountain and the 
Sinking of the sea: but, it is clear from examinations in Switzer- 
land, that the spread of the blocks must have been later than the 
formation of the present molasse-vallies,* which however we 
deduce from the last heaving process of the Alpine range ; that, 
Moreover, in the later epoch of the molasse formation, the sea in 
* Molasse is a term, descriptive of a soft green sandstone, occurring throughout 
the lower country of Switzerland.—Lyell, Principles of Geology, Vol. 4, p. 75.—Tr. 
