509 
When we recollect what great discoveries have been already made 
in the investigations of fossil botany by means of the microscope, 
and look to the inestimable value of the information obtained by 
Professor Owen, as to the structure of the teeth of fossil fishes, rep- 
tiles, and mammals, and see the wonderful results of the application 
of this new power to the examination of chalk and flint by Professor 
Ehrenberg, Mr. Lonsdale and Mr. Bowerbank, we may justly con- 
gratulate ourselves on the commencement of a new epoch in micro- 
scopic palzontology. 
GEOLOGICAL DYNAMICS.—GLACIAL THEORY. 
During the last year M. Agassiz has introduced a new and power- 
ful machinery into the Dynamics of Geology, by asserting the 
claims of ice to be admitted to the list of locomotive forces that 
have operated largely not only in forming morains (7. e. mounds and 
ridges of gravel and clay intermixed with large fragments of rocks) 
on the flanks and at the lower extremity of existing glaciers, but 
also in transporting erratic blocks with the detritus of morains to 
distant regions, and re-arranging them by the force of floods that 
originated in the melting of ice and snow. 
In the month of June 1840, a notice was read to us by him on 
the polished and striated surfaces of rocks in the beds of glaciers in 
the Alps; and another notice in the following November, on the 
evidence of the existence of glaciers in Scotland, Ireland, and En- 
gland. In the summer of 1840 he published in ‘Switzerland, in his 
‘Etudes sur les Glaciers,’ a description of facts which lie at the 
foundation of this question, illustrated by a splendid series of plates, 
representing the actual condition and residuary effects of existing 
- glaciers in the Alps. These phenomena are so essentially prelimi- 
nary to the investigation of the evidences of ancient glaciers in 
regions where they are now unknown, that no man is fully quali- 
fied to enter upon this question who has not prepared himself by 
the study of modern glaciers with a special view to their residuary 
phenomena, which have been overlooked, or referred to other causes 
by preceding observers in Alpine regions. 
After due acknowledgment of the discoveries of Scheuchzer, Gru- 
ner, De Saussure, Hugi, Venetz, and Charpentier, M. Agassiz exa- 
mines the origin of glaciers in the transformation of snow into solid 
ice, the different conditions of this ice in its various stages of ad- 
yancement, the causes of its movement, the history of the detritus 
that falls upon it and is transported along its surface and lodged in 
the form of morains upon its sides and at its lower extremity, and 
the modifications of these morains by the waters of temporary ponds 
and lakes formed upon and within the glaciers. He also investi- 
gates the action of modern glaciers in polishing and producing striz, 
ridges and furrows, and rounded bosses resembling wool-sacks 
(Roches moutonnés of De Saussure and Roches bosselées of Hugi), on 
the surface of the hardest rocks over which they pass; and also in 
grinding to the state of pebbles fragments of rocks that are forced 
along their bottoms, and in transporting to great distances large 
