TRAINS OF BLOCKS. 65 



more rounded, and there are not so distinct margins to the trains. One of us (c. H. H.) 

 refers to East Williamstown, where the granite bowlders are numerous, for an example. 

 We are not confident, however, that any of these cases ought to be regarded as the same 

 with those at Richmond and Huntington. 



Of all the phenomena of drift none have been more difficult to explain by any theories 

 in vogue among geologists, than these trains of angular bowlders. To make water the 

 sole agent, as some theories do, is the most unsatisfactory ; for this could not alone have 

 torn the blocks from their parent bed, and if it had been able to carry them forward at all, 

 it must have rounded them. The most plausible resort would be to glaciers ; but the na- 

 ture of the surface over which the trains have been strewed, forbids the idea of a glacier. 

 Common icebergs are no more satisfactory ; but if we suppose islands capped with ice, 

 and this occasionally torn up by the waves, and carried forward with fragments of rock in 

 their under side, torn off from the islands and dropped along the way, or perhaps ice-floes 

 in like manner frozen to the shore and torn off and urged along the coast, there is some 

 plausibility in the explanation. But fully to set forth the arguments, pro and con, would 

 require so much of detail as to the localities, that we judge it best merely to indicate our 

 preferences among the theories that have been proposed. 



We have sometimes been inclined to refer these "streams of stones" to what in Sweden 

 are called Osar (or osars as we should anglicize the word, although osar is the regular plu- 

 ral in the Swedish language of Os which means "a pile of gravel"), and which occur also 

 in Great Britain perhaps somewhat modified. These are streams of stones, gravel and 

 sand accumulated behind obstructions, such as a ledge of rocks, or a stranded iceberg, and 

 strewed along never more than a mile. But in Sweden these osars are confined to flat and 

 level regions, whereas our trainees stretch over our mountains and valleys obliquely, and 

 are many miles long, and are composed only of angular blocks. They may be varieties of 

 the osars, but they must have been produced by greatly modified causes, and we have not 

 found in Vermont any genuine example of the European Os, if we may judge from des- 

 cription. (See Murchison's Geology of Russia, Vol. I., p. 540.) 



STRIATION, PLANISHING AND EMBOSSMENT OF BOOKS. 



If the immense masses of detritus that cover the surface in Vermont, containing bowl- 

 ders weighing hundreds or even thousands of tons, have been driven forward either by 

 water or ice, they must have left traces of their transit on the solid ledges. They have 

 done so almost everywhere. Where the ledges have been exposed, however, for thou- 

 sands of years, these markings have often, but not always, been obliterated by the disintegra- 

 tion of the surface. There is great difference in this respect between different rocks some 

 almost bidding defiance to the action of the elements, while others are easily eaten away. 

 The calciferous mica schist that occupies so much of the eastern part of the State, is about 

 the poorest for retaining the striation and planishing of the drift. Coarse granite and 

 gneiss are about as bad. Crystalline limestone is quite as poor ; while silicious limestone, 

 such as occurs along the borders of Lake Champlain, has great power to resist decomposi- 

 tion. The upturned edges of clay slate are perhaps the best of all rocks to retain the 

 markings. But if the soil be removed to a considerable depth from almost any rock, we 



