GLACIAL DRIFT. on3 
observed in their position, shape, size, distance and direction of trans- 
portation, etc., including the various kinds of moraines. The striation is 
believed to correspond in direction with the course taken by the frag- 
ments in their travels. The stones usually proceed in right lines from 
their sources, at first in large rough blocks, then showing more abrasion 
and less size, till they have been reduced to pebbles or coarse gravel, 
and finally no traces can be seen of them. 
This method of dispersion shows miners how to search for veins of 
valuable ores. If blocks of copper or lead ore show themselves tempt- 
ingly, the country may be searched in the direction of the drift common 
to the neighborhood, usually visible on ledges near by in striz. Let the 
country be carefully explored in the direction whence the stones have 
proceeded, and when no more can be found, the soil may be removed, 
and the veins will show themselves. This method of search, both for 
veins and beds of rock, has been constantly employed in the conduct of 
the geological survey, and the principle has never been found incorrect. 
The existence of many peculiar ledges would never have been discovered 
had not attention been first drawn to certain singular boulders. 
If we were to take up the drift deposits one by one, or town by town, 
and specify what kind of boulders occurred, and what seem to have been 
their sources, much labor would be required, and the details would not 
be interesting. When the geology of the state is perfectly understood, 
those conversant with it will be able to say whence every stone found 
anywhere within our limits has been derived. The general law of the 
‘dispersion of the fragments may be thus stated: the boulders have been 
transported in the direction in which the ice of the glacier period moved, 
as indicated by stria. By consulting our table of striz, where nearly 
every town is represented, those seeking to learn the origin of interesting 
stones in their neighborhood may learn the probable point of compass in 
which to travel to find the source of their specimens. I will endeavor to 
state presently any exceptions to the above rule known to exist. 
‘The teachers of the institute at New Hampton have interested their 
classes in this subject, and the young people have left behind monuments 
to themselves in the form of large boulders transported by the drift, 
found in their neighborhood, and presenting some strange or unique 
feature. I noticed a large block of the handsome porphyritic gneiss 
VOL. HI. 33 
