MINERALOGICAL AND GEOLOGICAL NOTES. 



No. 7. 



evidences of sübsidence and elevation in essex 



county in recent geological tlme, as shown 



by Field Work at the Sea Shore. 



BY JOHN H. SEARS. 



(Curator of Geology and Mineralogy, Peabody Academy of Science, Salem.) 



While engaged in other work connected with the geol- 

 ogy of the county, I have noted such evidences of the 

 subsidence and elevation of the coast line as carae under 

 Observation and call attention to them now, hoping to 

 avvaken some general interest in this subject. 



First. The evidences of subsidence are clearly shown 

 along the entire coast line in many sheltered coves. At 

 Nahant, in the cove between Bass Point and the steam- 

 boat landing, covered by six to thirteen feet of water at 

 high tide, may be seen numerous stnmps of several species 

 of forest trees. Amonsj those which are well enousrh 

 preserved to be determined are white pine, swamp or 

 white cedar, hemlock, spruce, ash, oak and maple. The 

 roots of these trees are found in original leaf mould and 

 peat beds, from one to three feet in thickness, which rest 

 upon a very tenacious, slippery, blue clay of unknown 

 depth, the leaf mould and peat beds being covered by 



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