E. O. Hovey — Trap Ridges, etc. 361 



or three treatments with hypochlorite solution, gives up nothing 

 to cold nitric acid. It is almost wholly insensitive to light ; 

 because as fast as normal chloride is decomposed by light it is 

 reconstituted by the conversion of a corresponding quantity of 

 subchloride present, to normal chloride. The chloride and sub- 

 chloride are in an equilibrium which the action of light does 

 not alter. 



August, 1889. 



Akt. XLYII. — Observations on soms of the Trap Ridges of 

 the East Haven-Branford Region* with a ?nap (Plate 

 IX) ; by Edmund Otis Hovey, Ph.D. 



Contents. — - t The topography of the region — its trap belts and sandstone ridges — 

 general position and forms of the trap belts— particular description of Pond Rock 

 and the ridges east of it. Kinds of trap rock in different parts of the region — the 

 amygdaloidal trap and its relation to that which is non-vesicular. The relation 

 of the sandstone to the trap — contact phenomena. Main theories which have 

 been advanced to account for the occurrence of the trap — special discussion of the 

 theory of " contemporaneous overflow." The age of the trap. Conclusions. 



The character and age of the ridges of trap which occur so 

 numerously in the Triassic sandstone of Massachusetts, Con- 

 necticut and Kew Jersey are questions that have been dis- 

 cussed with more or less vigor for the last seventy years. In 

 the Bulletin of the Museum of Comparative Zoology, 1883, 

 Prof. W. M. Davis has given a valuable list of papers bearing 

 upon the subject. In this Bulletin, in this Journal, III, xxiv, 

 1882, and III, xxxii, 1886, and in the Seventh Annual Report, 

 TJ. S. G. S., 1885-86, just issued, he has detailed his own ob- 

 servations, illustrating them by figures and sections, and has 

 elaborated his conclusions as to the trap. The investigations, 

 the results of which are given in the present communication, 

 were undertaken by the writer in the hope of throwing addi- 

 tional light upon the perplexing question. 



The region most carefully studied in this connection lies to 

 the east and southeast of the city of New Haven, Conn., in the 

 towns of New Haven, East Haven, Bran ford and North Bran- 

 ford, and though small, being about eight miles in greatest 

 length, from southwest to northeast, by four miles in width, it 

 is full of interest topographically as well as geologically. The 

 general monoclinal eastward dip of the sandstone, with numer- 

 ous faults, gives long ridges whose general trend is that of the 

 strike of the strata; i. e , N. 10° or 15° E. Most of these 



* Presented in June, 1889, as a thesis for the degree of Ph.D. from Yale Uni- 

 versity. Read in part before the American Association for the Advancement 

 of Science at its Toronto meeting, 1889. 



