346 Notice of a Scientific Expedition. 



spect than Thomsonite ; they are not so long, and their external 

 , portions are weathered and partially decomposed, and often pass into 

 a variety of snow white asbestus. These snow white masses were 

 not seen to occur at any other locality, but are abundant at this 

 place. A broken mass of this substance presents numerous points 

 from which individuals diverge, so that in a single mass there is no 

 common centre of radiation. 



Heulandite. — This fine mineral is not so abundant at this locality 

 as those already mentioned. It is, however, frequently present in 

 the cavities of amygdaloid. Colors both white and flesh red. The 

 size of the crystals is good, varying from a quarter to three fourths 

 of an inch in the longest diagonal. Their beautiful pearly lustre 

 will always distinguish it from every other mineral. In some re- 

 spects the most interesting variety of Heulandite at this locality oc- 

 curs in long cylindrical cavities in the amygdaloid. These cylin- 

 ders are often about the size of a pipe stem, sometimes larger, not 

 smooth but beset with projecting points. It is usually the case, that 

 cavities formed in partially fused masses are oval or almond shaped. 

 May not cylindrical cavities be produced by currents of air forced 

 through the oval cavities in a continued stream, while the rock is in 

 a yielding state. 



The vesicular structure of amygdaloid is undoubtedly produced 

 by confined aerial fluid, and if this pent up air or vapor could find a 

 vent in one direction, the flowing of it in that direction might con- 

 vert all the vesicles into one contiuous cavity. 



Patridge Island, about one fourth of a mile from Parsboro, and 

 to which it is joined by a narrow ridge of sand, furnishes at present 

 but few minerals. We were informed by Dr. Gesner, an industri- 

 ous and successful cultivator of Nat. Science, that minerals, which 

 a few years since, were abundant, have now become scarce. The 

 truth seems to be that from its proximity to the village, this enchant- 

 ing little spot is much exposed to visits, hence every thing which 

 falls from the cliffs is soon carried away. We were unable to obtain 

 more than two minerals in any tolerable quantity, these were stil- 

 bite and calcareous spar. Chalcedony and a decomposed variety of 

 it, usually called cacholong, and a coarse red jasper, are common to 

 this, and most every other locality where trap rocks occur. 



The Stilbite forms an almost perpendicular vein in the amygda- 

 loid and greenstone three or four inches thick, and extends up the cliff 

 from thirty to fifty feet. Colors white and flesh red. It occurs in 



