I 82 NATUKK STUDY. 



marks. The cla}' was washed further down the valley 

 while the sand and water- worn rocks were left here. 



In the till are found bowlders of all sizes and kinds. 

 They are all strangers, brought from ledges farther north. 

 Bowlders of porphyritic gneiss that is not found near 

 Manchester in ledges are here abundant. Fragments of 

 mica schist that have long been safe from weathering are 

 now crumbling in the air. One large bowlder of quartz 

 was found that was crossed by several veins of a jasper}- 

 nature. In another place was found a large specimen of 

 conglomerate considerably metamorphosed. None of these 

 are found /;/ sitic near their present location. Numerous 

 scratched or polished specimens have been found and 

 carried off to illustrate the glacial period. This gravel 

 bank, located on Cilley street in Manchester, may be of 

 little interest to those living at a distance but it will serve 

 as a type of similar deposits found wherever the ice-sheet 

 went. They are of inestimable value to geography classes. 



The larger bowlders found upon the surface of the 

 ground everywhere in the north are always interesting. 

 They bring to our doors the ledges of other localities. 

 While the large specimens are of no more real interest to 

 the geologist than the smallest, they are more striking to 

 the observer and especially to children. Prof. Hitchcock, 

 in his geology of New Hampshire, describes many. Per- 

 haps the largest that has been found yet in this state is 

 the Churchill Rock of Nottingham, 62 feet long, 40 feet 

 wide and 40 feet high. It contains 75,000 cubic feet and 

 weighs about 6000 tons. 



The two bowlders figured in this number of Nature 

 Study are found near Manchester, and are probablj^ the 

 largest in this vicinity. In the southern part of Dunbar- 

 ton is a well rounded bowlder of porphyritic gneiss, 35 feet 

 long, 31 feet wide and 20 feet high. This stone rests in a 

 swamp apart from all other rocks. The height given was 



