East Haven- Branford Region. 379 



the overlying shale on the thin part. Again, there should be 

 close similarity between the rocks on each side of such small 

 dislocations as these are, if they were faults ; but the trap 

 rock in the necks is much more fractured in structure, than it 

 is either just north or south of them, which is a result of its 

 being thinner at the time of eruption and therefore more 

 rapidly cooled. 



The crescentic form of many of the outcrops of the trap 

 has called out much speculation as to its origin. The best ex- 

 amples of these " crescents " are Pond Rock and Toket Mt. 

 Prof. Davis advances the idea that the form is due to " a com- 

 bination of faults and faint dish-like folds,"* and would make 

 the ranges east of Pond Rock confirm the theory, saying that 

 the second range is but the eastward outcrop of the first, 

 brought up by the saucer-like synclinal. The facts do not ap- 

 pear to me to support this conclusion. His scheme demands 

 that the sandstone near the second eastern range should dip to 

 the west, while that below and above the southern portions of 

 the main sheet and the first eastern should dip northward. 

 But the sandstone on both sides of the main sheet in the rail- 

 road cut dip 16° south of east ; at the foot of the lake the 

 direction of dip is about the same, and there is no reason to 

 suppose that there is any change throughout the remainder of 

 the ridge, which is short and nearly straight. No outcrop of 

 the sandstone has been observed near the southern end of the 

 first eastern range, but the shales in the railroad cuttings just 

 east of the lake, and on the Branford turnpike very near the 

 crystalline rocks, dip high to the south of east. At two places 

 half a mile apart, near E 2, the sandstone is exposed with its 

 strike N. 45 E., and its dip at one place 60° and at the other 40° 

 toward the southeast, while the only/ westward dip observed in 

 connection with this range is in the old quarry east of the road 

 from Branford to " Cherry Hill," and this is probably due to an 

 overthrow by the trap. Fig. 1 was prepared from data ob- 

 tained in the field. Near the northern part of the main sheet 

 and the first eastern range most of the sandstone is conform- 

 able with the trap. 



Concerning Pond Rock and Toket Mt., which he considers 

 parts of one great sheet, Prof. Davis says : " Toket Mountain 

 is not separated from Pond Mountain by a fault, but by ero- 

 sion on a transverse flat-arched anticlinal, clearly defined by 

 the dip of the adjacent conformable sandstones." f A faintly 

 developed transverse anticlinal is called in to explain a slight 

 indentation in Toket Mt. north of its middle, and a large one 



*This Journal, III, xxxii. 347, 1882. Tn the 7th Ana. Rep't U. S. a. S., just 

 issued, this theory is more fully worked out. 

 •fThis Journal, III, xxxii, 347, 1882. 



