SEGREGATION. 



I learned, 



Fio. 44. 



Section of a Terrace in Vernon. 



that on penetrating the loam, on the extensive plain (terrace) in Westminster, a thick bed of 



gravel is found, and beneath the gravel a stratum 

 of blue clay, two or three feet thick, and beneath 

 this is quicksand. 



"Dea. Gray of Coventry informed me, that after 

 penetrating the loam and hard pan 40 feet, on his 

 farm, he struck a bed of very tough blue clay, six 

 jjj^gg thic]^ and that this rested on quicksand. 

 His well yielded an abundant supply of water for a 



few years, when it suddenly disappeared, and re- 

 mained dry ever after, till it was filled up." 



Fig. 44 represents an insulated hill of gravel and 

 clay, five rods long, in Vernon, near the meeting 

 house. It is on Connecticut River, and is doubt- 

 less one of its terraces. It is not usual to find so great a dip in strata of clay and gravel. 



We were much surprised to discover in strata of sand in North Dorset, a large number 

 of segregated veins. The locality is nearly a mile south of the railroad station, upon the 

 east side of the carriage road to Manchester. An excavation has been made in one of the 

 large piles of detritus filling the valley in the manner of a gorge terrace, by the removal 

 of the fine sand for economical purposes. In 1859 this excavation was three rods long 

 and about forty feet high. Fig. 45 gives some idea 

 of the appearance of the veins intersecting the strata, 

 over a part of the excavation. The strata dip five 

 degrees to the southwest, while crossing them at 

 various angles are the segregated veins. 



We measured veins inclining southerly both 46 and 22. Some are nearly perpendic- 

 ular, and rarely some are approximately horizontal. There were an immense number of 

 very small veins, not represented in the figure, which branched in every direction, and 

 were often anastomosed. The veins were made conspicuous by their elevation above the 

 surface of the surrounding sand, precisely as segregated veins now appear in metamor- 

 phic rocks. Were it not that they are harder than the materials in which they ramify, 

 their existence might not be suspected. 



These veins must have been superinduced after the deposition of the sand for there 

 has been no mechanical disturbance, and the materials of the veins does not differ appre- 

 ciably from the sand in the strata. For their origin we must perhaps look to the same 

 agencies which have produced segregated veins in the older rocks, i. e., chemical or 

 galvanic action. We can conceive of no other possible agency to have produced these 

 sand veins in North Dorset. 



We fear that this exhibition will not long show itself to visitors ; for only one year 

 after it was discovered, we visited it the second time, and found many of its features 

 obliterated. Nature and artificial excavation both conspire to produce this result. 



Fio. 45. 



