673 
for the transport of the very distant great blocks, we have to thank 
M. Necker for the additional materials, which seem to establish one 
fundamental fact in reference to the Alpine case, viz. when this 
detritus was cast off, the gorges and flanks of the chain had nearly 
the same reference to the central crest as that which now prevails. 
If this be proved, the theory which depends chiefly upon the sup- 
position, that a great elevation of the centre of the chain broke 
off the ice and dislodged the glaciers, is deprived of its chief basis. 
In what manner Professor Agassiz can account for the Alps being 
a great centre of dispersion when at a lower level, is indeed a part 
of his theory which is not easily comprehended. On the other hand, 
whatever we may think of M. Necker’s hypothesis, it must be ad- 
mitted that the facts adduced by him support one essential point of 
the glacialists, by connecting the presence of blocks with the exist- 
ence of glaciers in the Alps, the former being, as he states, inva- 
riably found both in the southern and northern watersheds of those 
mountains, and at the mouths of the great transverse ravines which 
lead up to the regions of perpetual snow, and in all such cases he 
allows that the condition of the blocks is highly indicative of their 
having once formed part of the “moraines” produced by former — 
glaciers. 
But the important point, that the glacier is the chief source of 
the origin of erratic blocks, is entirely denied by another antagonist 
to the theory of Agassiz, who has appeared in the person of M. 
Godeffroy *. 
After the observations of two summers in the Alps, this author 
has become convinced that the materials of the so-called moraines 
have not been derived simply by the glacier from the solid rock in 
the higher mountains, but are the re-arranged portions only of a 
great pre-existing diluviai deposit, which had been accumulated in 
the radiating valleys during a period of great disturbance, anterior — 
to the existence of glaciers in that latitude. Describing (like M. 
Necker) one of these “trainées” as having a continuous length of 
fifteen leagues, he infers that such a mass could never have been 
deposited by a glacier proceeding from mountains of no greater alti- 
tude than the Alps. Arguing that glaciers are merely the condensed 
or central portions of vast accumulations of snow, forced downwards 
into the gorges by increasing volume from above, the chief novelty 
of M. Godeffroy’s work is contained in the opinion, that in advancing, 
these bodies of ice cut through the ancient diluvium or drift, just 
as a plough-share cleaves the soil (“‘presso tellus consurgit aratro” 
being his motto), and threw up some portions into lateral moraines, 
as well as pressed before them others to form terminal moraines. 
_ To the crystalline and mechanical changes which the snow has 
undergone in its passage into solid ice, is attributed much of the 
confusion and irregularity of outline so visible in the “aiguilles” 
and other icy masses of the Alps; and to the same disturbing ac- 
tion is referred the rounded and worn exterior of the boulders in 
* Notice on les Glaciers, les Moraines et les Blocs Erratiques, 1840, 
VOL. III, PART II. — sii 
