EXTRACTS FOREIGN AND DOMESTIC. 15 1 



In answer to questions, Dr. Jackson stated that the base of the 

 trap rock agreeing with the sandstone, prevented any great dis- 

 jturbance when the former passed through the latter, whilst the 

 [fineness of the sandstone accounts for the cellular nature of what 

 trifling portions of amygdyloid is found at the point of contact. 

 He fully agreed with Mr. Dana, that the agency of hot water 

 was employed by nature to fill up the cavities of trap rock mine- 

 rals with crystals by deposition. lie also instanced the beautiful 

 arrangement by which when trap rock passed through gradual 

 limestone, and the raetalic oxides were present, we have all the 

 \aricties of cinnamon and other garnets, according to the modifi- 

 cations of the oxides ; by the fusion of that limestone in contact 

 ivvith its walls. And he instanced the fact that wherever these cin- 

 pamon garnets, &c.,are found in the loose soil, it is an evidence 

 hat limestone is close by, and is thus a valuable guide. Dr. 

 lackson placed the rocks in the following order of age. The oldest 

 A as the porphyry ; next the porphyiitic traps, then the blue trap, 

 hen the brown trap, then the bastard containing olivine, &c. And 

 |t is curious to see the many different points of the compass to 

 jvhich these different series bear ; the porphyry runs from nearly 

 puth to north ; the porphyritic trap, from S. W. to N. E. ; the 

 )lue trap, from W. S. W. to E. N. E. ; the brown trap, nearly 

 iist and west ; and the basalt from E. S. E. to W. N. W. ; thus 

 ifoing all round the compass ; and of course the various different 

 jeries of trap rocks must frequently intersect and cut through each 

 ither, and at Bald Head, York ; and at Rye, near Portsmouth, N. 

 T., we have very fine specimens of these interesting trap dykes. 

 )r. Jackson also spoke of the fact, usually overlooked, that sea 

 .ater from all parts of the earth contains phosphates. Every speci- 

 Aini of water brought home by the exploring expedition, gave this 

 esult. He had analyzed the hot w^aters of the Geysers, and found 

 boracic acid therein ; the silica there was held in solution by 

 austic soda; on exposure to the air, the soda, absorbing carbonic 

 eld from the atmosphere, becomes carbonate of soda, and the sili- 

 a falls down in a solid mass. 

 Mr. Dana had previously related the singular fact, that silica re- 

 luins in a semi-fluid state long after deposition, and is thus easily 

 iermeable by solution ; oil and water it was well known would 

 liter through chalcedony, and it was in this way that quartz and 

 lalcedonic geodes contained in their centre other and very diffe- 

 ■iit mineral substances in a beautiful crystalized state. 

 Prof. Silliman produced a fine specimen of native copper found 

 :ar Wallingford, Conn., where the trap had passed through the red 

 mdstone, and a mass of one hundred pounds weight had been thus 

 lund. 

 Mr. exemplified the agency of hot water in producing 



