1886.] NE-\V YORK ACADEMY OF SCIENCES. 17 



is the result of the decay of the underlying serpentine. I had 

 regarded ic as a deposit from springs, but am now inclined to 

 believe that Dr. Hunt is correct in his view, and that these ores 

 have originated in a similar manner to that which has produced 

 other Appalachian limonites ; though the presence of much sili- 

 ceous matter with the ore and of magnetic iron sand, in some of 

 the deposits indicate that deposition from solution may have 

 produced some of the material, and the black sand must have 

 been mechanically washed in. 



Glacial Drift. — On my geological map published in the An- 

 nals, Vol. IL, plate xv., the southern boundary of the Glacial 

 Drift is indicated by a dotted line. I have since retraced this 

 line, but have no essential alterations to make in it. 



The construction of the deep cutting and tunnel for the 

 Staten Island Rapid Transit Railway, at Tompkinsville, has ex- 

 posed a most interesting section through the Glacial Drift. 

 This is seen to be truly morainal in its upper portion, consisting: 

 of large angular boulders and pebbles irregularly imbedded in 

 unassorted clay and sand. Tiie lower part of the bank is, how- 

 ever, beautifully stratified and the materials composing it are 

 sorted into bands and layers of different substances, strata of 

 sand of several degrees of coarseness, others of clay, and still 

 others of pebbles ; very few boulders occur in this lower part, 

 and these are in special well-marked bands and are more rounded 

 than those above. 



Wiiile this exposure is of great interest as illustrating the dif- 

 ference between morainal and stratified drift at a glance, it is of 

 much greater importance as furnishing a measure of the depres- 

 sion of the coast at this point during the Glacial Epoch : for the 

 altitude of the upper line of stratification above tide gives us 

 the comparative position of the coast as regards its position in 

 Glacial times. This is between 25 and 30 feet. Hence we may 

 safely conclude that during the presence of the great ice sheet 

 the shores of New York Harbor stood at least that amount lower. 



As is well known, the coast is at present suffering depression. 

 How much higher it has been since the retreat of the glaciers, 

 or to how many oscillations it has been subjected since that 

 time, are fair subjects for speculation, but cannot now be satis- 

 factorily answered. I have observed the stratification of the 

 drift at other places in the vicinity, but nowhere have I seen 

 such a beautiful exhibition of it as here. 



Nearly Driftless Areas North and West of the Terminal 

 Moraine. — This is a feature of the glaciation of the region 

 which was not apparent to me until a year or so ago. There 

 are at least two of these on Staten Island. One is on Pavilion 

 Hill, at Tompkinsville Landing, where there are but very few 



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