120 J. D. Dana — Ghhritic formation west of New Haven, Conn. 



This slaty variety of the rock continues with little change 

 for a mile and a half north. Beyond, the massive layers 

 increase in extent. At the deep Derby railroad cut, two miles 

 north of Savin Rock, the massive variety constitutes more than 

 half of the rock exposed in the sections; and it is not all 

 in separate beds; for thick beds that are slaty in one part are 

 in others for many rods massive, and it is impossible to separate 

 the massive from the slaty by any stratigraphical planes. 



This massive rock is commonly without a trace of bedding; 

 at the same time, it is variously and extensively jointed, so that 

 it affords only deceptive indications of strike or dip. It varies 

 in color from greenish gray to dark olive-green and blackish 

 gray. Some of it is almost cryptocrystalline ; but in general 

 the texture is fine granular. Part of it is porphyritic with 

 small crystals of a whitish feldspar. 



Between this Derby cut and "Maltby Park," a mile and 

 three quarters west of north, this massive rock constitutes 

 nearly all the outcrops : and in some places the porjjhyritic 

 variety is pale greenish gray, from the thickly crowded feldspar 

 crystals. 



Over Maltby Park the rock is again slaty and silvery, often 

 with blotches of chlorite — a chloritic hvdromica slate — as at 

 Savin Rock; yet with enough of both the ordinary and por- 

 phyritic massive kinds among the slaty layers to exhibit its 

 close relation to the rocks farther south. The slate occasionally 

 has the chlorite in large lenticular concretions, and now 

 and then is light gray and contains crystals of pyroxene. In 

 some places, especially along seams, it is epidotic. Veins and 

 In the slate there are inter- 



_-.--.. -- _ _n of the limestone contains 



serpentine and is a handsome verd-antique marble ; and with 

 the serpentine there are often grayish green cleavable pyroxene 

 (aahlite), asbestus and chromic iron, 



A mile farther north, or five miles from Savin Rock, (west of 

 Westville), the rock is almost wholly a dark green chlorite 

 slate — the micaceous part absent. 



The rocks in the coarse of the five to six miles are — in reca- 

 pitulation — commencing at the Sound : 



For 1^ miles, chloritic hydromica slate, little of it massive. 

 1| to 2| miles, chloritic hydromica slate, much of it massive. 

 2i to 4 miles, massive chloritic rock with little of it slaty. 

 4 to 4f miles, chloritic hydromica slate, very little of the rock 



4f to 6 miles, mostly dark green chlorite slate. 

 It is to be noted that throughout the formation the slaty and 

 massive portions are so associated, sometimes as alternatmg 



