368 E. O. Hovey — Trap Ridges of the 



tact with the eastern sandstone, and the latter is from near the 

 middle of the ridge, and both are from the cut made by the 

 wagon road from Bran ford to Cherry Hill (at B on the map). 

 No. 2a is of a very finely crystalline rock, hard and lustrous, 

 and breaking with conchoidal fracture. Under the microscope 

 the rock shows less alteration than No. 23. The augite has 

 suffered the most from hydration, though many crystals show 

 their characteristic colors and cleavage lines, and very little 

 chlorite has been formed. The feldspar shows very little alter- 

 ation ; it occurs in its usual form — thin lath-shaped twin crys- 

 tals, each of which is made up of but two individuals. Much 

 magnetite appears, some of which is arborescent in form, the 

 octahedral crystals being connected along their cubic axes. 

 The trap of No. 15 from the contact shows more alteration 

 than the section just described, the augite being entirely de- 

 composed and more chlorite appearing, the feldspar also has 

 suffered from alteration. Of the other members of this range 

 some show the effects of much decomposition, while most are 

 composed principally of dense, sub-lustrous trap. 



The amygdaloidal trap and its relation to that which is 

 non-vesicular. — Much amygdaloidal trap occurs in the East 

 Haven Branford region, and while most of what is exposed is 

 on the upper or concave side of Pond Rock, it is by no means 

 confined to that position. The first aud second members of 

 the Pond ridge show a band of amygdaloidal trap six inches 

 wide at the lower contact wherever this is exposed. The 

 amygdules are of calcite. Amygdules of prehnite and calcite 

 have been observed in the first range east of this. Prof. Davis 

 says that no dikes are amygdaloidal in character,* defining a 

 dike as trap crossing the strata of sandstone or shale more or 

 less obliquely. In the second railroad cut east of Center 

 street, Fair Haven East (G, on the map), there is a typical 

 dike twenty-three feet wide. Four feet from the southeastern 

 wall of this dike a band nine inches wide, containing amyg- 

 dules of calcite and amethystine quartz extends in a line par- 

 allel with the wall of the dike. The band does not appear 

 to be a vein. Section No. Id is from this band of amygda- 

 loid. The trap shows much more alteration than appears in 

 Prof. Dana's section from the compact trap of the same 

 dike. No augite is perceptible and much chlorite has been 

 formed. A great deal of magnetite is present and most, 

 if not all, of it is crystalline. The chlorite occurs dissemi- 

 nated through the rock and in the amygdules. The amygdules 

 are various ; some are all chlorite, others calcite with a border 

 of chlorite, or vice versa ; some are of quartz inclosing chlorite, 

 or of calcite fringed with some zeolite, while others have quartz 



*This Journal, III, xxiv, 346, 1882. 



