Trans. N. Y. Ac. Set. 



118 



Apr. 30, 



drying-, it falls to a fine powder, most of which will pass through a sieve of 

 sixty meshes to the inch. It is composed of a mixture of about equal 

 parts of a porous earthy substance and of grains or crystals of quartz. 

 These crystals are frequently two or three lines in length,- quite pure 

 and transparent, and of simple habit ; often their edges are rounded 

 and show signs of abrasion. Whether they contain fluid-cavities or 

 not, has not been determined. In places a few pebbles and sharp frag- 

 ments of trap occur, besides a fair representation of all the formations 

 below it, especially of Potsdam sandstone ; of granyte no fragments 

 characteristic of any particular locality were found. 



The strata thus conditioned lie against the trap, and have a thickness 

 of about two hundred feet ; overlying them is a hard, light colored 

 granular sandstone. Their dip, and that of all the sandstone exposed 

 here, is 20° to N. 50° W. The trap stands at an inclination of about 

 80°, and at its contact the sandstone shows no marked signs of fusion. 



There are a few other localities in the State where the sandstone is 

 similar to this, viz. : about four miles from Trenton, and at two points 

 north of the locality at New Durham. In the reports of the State geo- 

 logical survey they have been termed " crumbling sandstones," and 

 described as a mixture of quartz-grains and of a decomposing feldspar. 

 Samples were collected at New Durham in such a manner as to fairly 

 represent the formation from the contact with the trap, and between 

 this and the trap, at several points. The trap was also analyzed, and 

 the results are given in the last column of the following table. Anal- 

 yses of characteristic unaltered sandstones, made some years ago by 

 Dr. P. Schweitzer, are also given for comparison. The alkalies were 

 determmed by Dr. J. Lawrence Smith's method, and the remaining 

 constituents by fusion with carbonate of soda. Iron was estimated 

 volumetrically. 



