TNTICRfJr.ACIAI, DKrosi'lN IN ('( )\ N i:("II('r'r vai.lky J) 



blendo-aiKlositos of nitlier basic characUM-, having' a holtxtrystalliiu; porphyritic 

 texture witli plieiioery.sts of aiidejiine-labradorite, bawiltic hornblende, aay;ite, 

 magnetite, and apatite "in a pilotaxitish <?roun(bnas.s of oligoclase-andesine and 

 niairnetite. These roeks are rarely fresh, but »?enerally very inneh altered— a fact 

 which renders them dillicnlt as well as unsatisfactory material for investi<^ation. 

 In many cases the tlecomposition lias been caused lar^iely by the action of ore- 

 bearing solutions, an exami)le of which is especially noticeable in analyses V 

 and IX. 



The fourth paper presented was 



EVIDENCES OF IXTERGLACIAL DEPOSITS IN THE CONNECTICUT VALLEY 



BY CHARLES II. HITCHCOCK 



[ A hstract\ 



The evidences of interglacial deposits in the Connecticut valley are derived 

 from the study of the eskers, notably the one passing through Hanover, New 

 Hampshire, which has been followed for thirty miles between Thetford and 

 Windsor, Vermont. The esker was formed in caves or open gorges while the 

 ice was still moving down the valleys, and it represents glacial action. Hence 

 the underlying deposits re{)resent what was earlier or interglacial. In searching 

 for the base of this esker I foiitid it to be modilied drift. It is mainly a compact 

 clay containing the curious massive concretions described in the "Geology of Ver- 

 mont" as coming from Sharon. This I find at several localities in the village of 

 Hanover, revealed by recent excavations. There is a later widely disseuTinated 

 clay not indurated and passing into silt, besides containing tubular ferruginous 

 concretions, which belongs to a later period. Besides the clay I discover a thick 

 sand higher up, and hence intermediate between the lateral terraces and the till, 

 which seems to represent an older deposit. Dunes blown from this were described 

 by Upham^ in Lebanon, Plainfield, Cornish, Charlestown, etcetera, always on the 

 east side of the valley. The dunes are absent from the west side of the valley, but 

 the deposit is present, sometimes associated with a tough clay. 



This lower clay has been tilted and contorted, as in the vale of Tempe, where 

 the wrinkling is comparable with the minute corrugation of crystalline schists. 

 The combined induration and folding are regarded as effects of pressure induced 

 by the overlying glacier. 



For two miles along the east bank of the Connecticut this esker is continuous at 

 a uniform height, cut across by Mink brook, Tempe brook, and at length by tlie 

 main river. I find valleys of drainage pointing across this ridge at two points 

 where artificial excavations have been made — one for a road to cross the Ledyard 

 bridge and the other for a sewer a mile north. The drainage must have taken 

 this direction before the formation of the esker and through modified drift. 



These facts confirm the correctness of my contention of the existence of a local 

 Connecticut glacier subsequent to the general southeasterly movement of the ice. 

 The presence of what appears to me to be this same glacial lobe is predicated by 

 the observations of Professor B. K. Emerson in Monograph XXIX of the United 



♦Geology of New Hampshire, part iii, page 41 et passim. 

 II— Bull. Geol. Soc. Am., Vol. 12, 1900 



