334 
GEOLOGY OF THE FOURTH DISTRICT. 
Northern New-York, I have seen examples where a slide or avalanche of snow and ice has 
brought down from a mountain side an immense number of fragments of the dark felspathic 
granite, freshly torn from the rock in place. These are precipitated into a narrow gorge, 
or the channel of a stream ; succeeding floods bring down other fragments, which are rolled 
along with the previous ones ; the water freezes, and, on breaking up in the spring with the 
melting snows from the higher grounds, forms an impetuous flood, which drives all before it 
in one general melee. In this way the angles are soon worn off, and every successive flood, 
or breaking up of ice and snow, helps to transport them farther down the stream, reducing 
their angles and their dimensions. In the beds of some of these streams, less than ten miles 
from their source, I have seen thousands of boulders of all dimensions from a pebble to the 
size of several tons. If these find their way to situations where they may be transported in 
floating ice, they are already perfectly rounded ; and it is easy to conceive how those previous¬ 
ly rounded in this way may be intermingled with angular fragments which have not been 
subjected to attrition, and both be deposited together. 
Means of transport, conditions, etc. of the surface. 
We have now to inquire by what means these blocks have been removed to their present 
position; and whether we have any other knowledge of the conditions of the surface at this 
period, which will enable us to decide, with any degree of probability, what agencies have 
operated. 
From the fact already stated, that these masses for the most part lie upon the surface, 
though sometimes buried beneath the drift, we are led to the conclusion that they were not 
moved by any powerful flood, such as has sometimes been supposed ; for, in this case, they 
would inevitably have been mixed with the loose materials of the surface which underlie them; 
and if a flood, with a force sufficient to transport these masses, had passed over the surface, 
the whole superficial deposit previously existing would have been swept off. Without the 
necessity of any farther reasoning in this place, we are led to adopt the opinions advanced by 
numerous writers, and supported by modern analogies, viz. the transportation of blocks of 
granite and other rocks enclosed in masses of ice. 
In all situations where glaciers from mountain regions come down to the sea, they float off 
in large masses, and even great tracts, bearing with them the accumulated fragments of rock 
and earth which they have gathered up in their passage. River and lake ice may do the 
same at the breaking up of a northern winter; and in this manner large quantities of rocks 
and earth are annually transported many miles from their original position, to be deposited 
only when the iceberg shall be stranded upon some coast, or the bottom of a shallow sea ; or, 
passing into a warmer climate, it is gradually melted, and precipitates its load to the bottom. 
Tins subject is ably treated in Mr. Lyell’s Principles of Geology, and in the concluding 
portion of Mr. Murchison’s Silurian Researches. 
It remains for us to inquire what were the conditions of this portion of the continent at the 
period in which these boulders were transported, and whether modern analogous conditions 
