GLACIAL DRIFT. 253 



observed in their position, shape, size, distance and direction of trans- 

 portation, etc., inckiding the various kinds of moraines. The striation is 

 beheved 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 striae. 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 striae. By consulting our table of striae, 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. in. 33 



