Dewey on Geology of Williamstown, 4rc, 345 



gneiss to the east, and rises again in Hampshire County, 

 " supporting the same rock of gneiss ;" but where it reappears, 

 the granite contains *' many imbedded minerals." This section 

 corresponds generally to the place and character of the mine- 

 rals in any section across Berkshire county. There are, 

 however, some peculiarities which may be mentioned at a fu- 

 ture day. The colouring corresponds to that on the geologi- 

 cal map in Cleayeland's Mineralogy. 



C. DEWEY. 

 Williams' College, Jan. 27, 1819. 



P. S, I have a part of a rock crystal, which contains, in a hol- 

 low, a liquid and a little air, and some black or brown particles, 

 which just sink in the liquid. It was found several years since 

 at Diamond Hill in Cattskill. This hill is only a small emi- 

 nence on the bank of the creek at that place, composed of 

 limestone, (if I have been correctly informed,) between the 

 strata of which, and on the side next the creek, this and other 

 rock crystals were found. I believe, Sir, you have one like 

 the above, obtained from the same place. The crystal, which 

 was generously given me by Mr. Van Loon, who found it, is 

 only a part of two crystals connected at their bases. Partly 

 under one of the solid angles formed by the united pyramids, 

 is the hollow, about f inch long, about | filled with the air, and 

 about ^ inch wide. The principal curiosity about it is the 

 liquid. It has never been known to freeze. It was exposed 

 yesterday morning an hour to an atmosphere 4 and 5 de- 

 grees below zero. It became less fluid, for the bubble of air 

 moved with less ease and rapidity. Still the liquid was fluid. 

 Its colour, which is naturally white, had a slight tinge of yellow. 

 The Rev. Mr. SchaefFer of New- York supposes the black par- 

 ticles are bitumen. Is it possible the liquid is naptha ? This 

 oil is sometimes colourless, and does not congeal at zero, and 

 that which I distilled from the Seneca oil, does congeal at 

 some degrees below zero. It can hardly be salt water, unless 

 it be very salt, and even then, it would have congealed at the 

 temperature of the air yesterday. What way can be devised 

 to ascertain what it is ? 



Jan. 30, 1819. 



