OF ARTS AND SCIENCES. 271 



Strata superincumbent on them, and enable their elements to 

 rearrange themselves and crystallize, while, at the same time, 

 the shales were not essentially changed in structure. He could 

 not conceive of so intense a heat passing through the shales 

 without annihilating every trace of organic life in them ; he 

 should certainly not expect to find any carbon except in the 

 form of graphite. 



Professor Agassiz replied to the last observation of Mr. 

 Bouve, that the coal in these rocks is partly graphite, very 

 similar to that found in Worcester. 



Dr. Jackson stated several facts which he considered irrec- 

 oncilable with the views maintained by Professor Agassiz. 

 He said that no trace had ever been observed of sandstone 

 passing into sienite, and that sandstone contains no potash or 

 soda, while these substances exist abundantly in sienite. He 

 dissented from the opinion formerly advanced by Mr. Agassiz, 

 that the nodules found in the rocks at Nahant are the remains 

 of corals ; and stated that they had been found, by microscopic 

 examinations, not to be organic remains. 



Professor Agassiz endeavored to account for the presence of 

 potash and soda in the sienite, by supposing them to have 

 been derived through the agency of heat, from the coal in- 

 cluded within the slate. He also stated, that he had found 

 one of the nodules to possess the structure of an Astrasa. 



Dr. Jackson replied, that sandstone is an exceedingly poor 

 conductor of heat, and may be heated to a white heat without 

 undergoing chemical change ; and he thought it impossible 

 that it should have been changed through its entire thickness 

 into sienite by heat, — potash and soda transmitted through 

 slate from underlying coal. 



Professor Peirce remarked, that the recent solar eclipse of 

 July 28, 1851, had proved quite a triumph for the new lunar 

 tables employed in the construction of the Nautical Almanac, 

 in comparison with those of Burckhardt, with which the Eu- 

 ropean ephemerides were computed. Both in this country 

 and in Europe the errors of theory had been reduced, from 



