684 
The presence of Mr. Lyell at this time in North America, is in- 
deed, most opportune, for whatever changes his mind may have re- 
cently undergone, no geologist has more strenuously laboured to 
make himself master of all its bearings, or more systematically en- 
larged our knowledge of this disputed subject. Possessing as he 
now does the advantage of observation on a large scale, I have little 
doubt that he will account for the wide dispersion of blocks in 
America from N. to S. by referring to a cause quite as general and 
quite as aqueous as that by which he originally sought to explain 
the phenomenon in Europe*. 
_ Although the consideration of this subject has already carried me 
beyond the limits I had prescribed to myself, yet I cannot quit it 
without reminding you, that the greatest geological authorities on 
the continent, led on by Von Buch who has so long studied these 
phenomena in his native land, are opponents to the views of Agas- 
siz. Even whilst I write, I find that M.de Beaumont has just com- 
municated to the Institute of France, a report on the results of a 
journey through Lapland, Finland, and the north of Europe, by his 
countryman M. Durocher, in which grouping the facts with great per- 
spicuity, he handles the whole subject with his usual master’s hand, 
and points out the value of the previous observations of Von Buch, 
Brongniart, and other writers. M.Durocher conceives that the phe- 
nomenon of the transport of erratic matters has proceeded from two 
successive and distinct operations: the first a great current from 
the pole, to which the striz and polish of rocks, and the deposits 
called Osars are referred ; the second, the transport of the distant 
blocks by vessels of ice, when all that part of Europe which they 
cover was subjected to the immersion of an icy sea. He does not 
agree with M. Bohtlingk, that the point of departure of the current 
can be placed in Lapland, but supposes it to have proceeded directly 
athwart those regions from the polet. But the point to which I 
* See Principles of Geology, 2nd edit. vol. i. p. 342; and Elements of 
Geology, Ist edit. p. 136. 
+ M. Durocher has made two valuable observations in showing us that 
the striated and polished surface of the hard rocks is sometimes covered by 
accumulations of sand and detritus; and that although proceeding in a 
general sense from the north, the furthest transported blocks are so distri- 
buted as to indicate radiation from certain mineralogical centres, much in 
the same way as our blocks of Shap granite have, on a less scale, been 
scattered from one point of distribution. In stating, however, that in the 
progress of these transported masses to the south, granitic blocks always 
constitute the outermost zone, it appears to me that M. Durocher has ge- 
neralized beyond the field of his own observation. In Russia, for example, 
M. de Verneuil and myself traced greenstone blocks to the same southerly 
latitudes as granites. The blocks between Jurievitz and Nijny Novogorod 
are composed of quartz rock and of the peculiar trappzean breccia known in 
Russia as ‘“‘ Solomenskoi-kamen,”’ the parent rocks of which we examined 
in situ near Petrazowodsk (Geol. Proceedings, vol. iii. p.405), whilst the 
extreme boundary of these boulders extends to Garbatof on the Okka, S.W. 
of Nijny Novogorod, and consequently very far beyond Kostroma, the limit 
assigned to them by M. Durocher. Again, if M. Durocher prolongs the 
