234 On the Geography and Geology 



rectangular branches. These veins consist of two tables, sepa- 

 rated by a rift in the middle, and each bending round, without 

 fracture into the ramification. The fibres composing these tables 

 are perpendicular to the axis of the vein ; seldom oblique. 3, Veins 

 of white rhombic calcspar are not unfrequent, with facets, an inch 

 or more in diameter, passing across the strata, and often parallel 

 to them for long distances. They are from two to six inches wide, 

 but often expand in a lenticular form, and then sometimes contain 

 a small mass of the amygdaloid in which they are placed. They 

 are most common near the conglomerate at Point Marmoaze. On 

 the outer woody isle off this point, there is a vein of this mineral 

 invested and penetrated by large masses of green earth. 4. Veins 

 of quartz in two adhering parallel tables are occasional, whickhere 

 and there open, and exhibit druses of quartz crystals, seldom of 

 amethyst. 5. A vein of amygdaloid, three inches broad, with 

 well defined and nearly parallel sides, of the same kind as that 

 supporting the conglomerate of Point Marmoaze, crosses a ridge 

 of amygdaloid a few hundred yards from that conglomerate. It 

 is about five feet above water-mark ; and is of a dark colour, and 

 very full of almonds of calcspar, frequently coated with zeolite. 



The imbedded substances of this amygdaloid are various and 

 plentiful. They are calcedony, bluish white ; calcspar, red, white, 

 and green; zeolite; stilbite; prehnite; rock crystal; amethyst; 

 agate, striped and fortification carnelian, green earth ; copper 

 pyrites ; green carbonate of copper and plumbago. The greater 

 part of these are usually coated with green earth. The four first, 

 and green earth, are sometimes in such quantities as to constitute 

 the greater part of the stratum. There is a black amygdaloid 

 three miles below Point Marmoaze, full of small vesicular druses 

 lined with very brilliant rock crystals and botryoidal calcedony. 

 In such druses the prehnite occurs, in mammillary coatings. 

 Calcedony and zeolite are most abundant two miles below Point 

 Marmoaze : agates and carnelian (amber-yellow and pale red,) a 

 mile and an half lower down. I there saw the remains of two 

 splendid groups of quartz crystals, 10 inches in diameter. Red 

 zeolite often forms, hereabouts, small naked and solitary deposits 



