230 THE AMERICAN MONTHLY [October, 



Diatoms of the Connecticut Shore. — II. 



By W. A. TERRY, 



BRISTOL, CONN. 



The salt meadows or marshes of the Connecticut shore, as far as 

 I have been able to examine, consist of a bed of coarse peat some 

 four feet in thickness, lying upon a marine deposit of whitish clay 

 and sand containing diatoms. This deposit is sometimes over 

 thirty feet thick and occupies the bed of ancient estuaries. The 

 rocky ridges near New Haven are mostlv trap dikes, but at Fair 

 Haven is an outcrop of the old red sandstone ; eastward, at Stony 

 Creek and Leete's Island, the rocks are granitic, somewhat resem- 

 bling the so-called Scotch granite. The Qiiinnipiac meadows are 

 northeast of New Haven, and extend from Fair Haven to North 

 Haven ; being five or six miles in length, and about one and a half 

 miles in breadth, having eight or ten square miles of surface which 

 is under water at high tide. Through this marsh the Quinnipiac 

 River winds it sinuous course. On its western margin, on the 

 line of the Hartford and New Haven R.R., are numerous brick- 

 yards, which procure their clay from pits of considei'able size dug 

 in the marsh, from which the tide is kept out by dikes and which 

 are drained by steam pumps. On the west and north the clay 

 bed is overlaid bv ordinary drift, but on the east and south it runs 

 under the marsh. The '■•fat" clay used for bricks is laid down 

 in undulating strata, varying some six or eight feet in height. 

 Upon this is a mixture of similar red clay with sand called '' delf," 

 whose surface and strata are nearly horizontal. Upon this clay 

 lies a bed of coarse white sand from two to four feet thick ; neither 

 clay nor sand contains any diatoms. Upon the sand is a deposit 

 of black alluvium about one foot thick contaming yres/i-wa^er 

 diatoms. On this is a stratum of loam containing the roots of trees, 

 with their trunks lying beside them, the whole covered with about 

 four feet of coarse peat and two feet of water at high tide. 

 Among and upon the tree trunks is a deposit of white clay and 

 sand containing marine diatoms, and this extends upw^ard 

 through the peat to the surface. The stratum of fresh-water dia- 

 toms is therefore about eight feet below the present sea level, and 

 is covered with about six feet of marine deposit. The fresh-water 

 deposit is not rich, and the forms are much broken ; Pinnulaj-ia 

 lata being the most abundant and almost the only one remaining 

 entire, although fragments of other Pinmdaria and of Stauro- 

 neis acuta are plentiful. The marine deposit varies considerably, 

 some parts of it being very rich ; deep-water forms are more 

 abundant at the bottom, and brackish-water near the top. It ap- 

 pears evident that this region once occupied a higher level, and 

 after the glacial period, was the bed of a fresh-water lake, which 

 filled up or was drained and became dry land covered by a young 

 forest growth, then suddenly sank and was submerged beneath 

 tidal waters ; the trees died and their trunks decayed at the water 



