234 ANNUAL OF SCIENTIFIC DISCOVERY. 



THE TACONIC SYSTEM. 



At a meeting of the Boston Society of Natural History, in De- 

 cember, 1867, Rev. Mr. Perry read a paper upon the red sand- 

 stone of Vermont, and its relations to other rocks. Mr. Perry 

 claimed that the red sandstone was the equivalent of the Potsdam 

 sandstone of the New York geologists, and that the adjacent 

 formations to the eastward were not highly metamorphosed rocks 

 of a more recent period, as has been constantly asserted, but were 

 older than the red sandstone, and lay unconformably beneath it. 

 These opinions were the same in general as those persistently 

 though unsuccessfully urged by the late Dr. Emmons. Mr. Perry 

 further maintained that the beds underlying the red sandstone 

 could not be considered as an extension of Potsdam sandstone 

 downward, but that with it they constituted a grand division of 

 rocks, to which Emmons's name of Taconic might be applied, and 

 which was equivalent to the "Primordial Fauna " of Barrande. 



The Potsdam sandstone was the uppermost member of this 

 group, and clearly distinct from the overlying lower silurian or 

 Champlain system. By a careful study of the rocks in place, and 

 of their limited series of fossils, Mr. Perry had discovered that the 

 Taconic system, as developed in north-western Vermont, was 

 divisible into three groups, stratigraphically unconformable to 

 each other. The lower division consisted of talcoid slates and 

 conglomerates, and was destitute of fossils ; the middle should 

 probably be separated into two series, the black slates and the 

 Georgia slates, each with its distinctive fauna ; the fossils of the 

 upper division, or Potsdam sandstone, again represented new forms 

 of life. 



ATMOSPHERIC ACTION. 



The carbonic acid of the air slowly attacks the rocks above the 

 ocean level, and thus turns them to clay, forming carbonates with 

 the soda, potash, lime, and magnesia set free, and carries these 

 down as carbonates to the sea, where the carbonate of soda decom- 

 poses the chloride of calcium of its waters, and forms common salt 

 and carbonate of lime. This series of actions is the source of the salt 

 of the sea, of all clays, and of limestones which are chemical and 

 not organic in their origin. Organic living things do not generate 

 the carbonate of lime, but appropriate it, when formed for them by 

 chemical reactions ; and thus great portions of our limestone rocks 

 are marie up of fossil remains. In 44 feet of limestone, there is 

 separated and condensed from the air a large atmosphere of car- 

 bonic acid gas; the early atmosphere was therefore very dense 

 and unfit for the sustenance of the higher forms of life, until by 

 far the greater portion of this gas had been removed by the forma- 

 tion of the carbonate of lime and vegetable matter now con- 

 stituting coal and petroleum. 



GLACIERS IN THE TROPICS. 



Dr. Newberry, in remarks on the facts which had been consid- 



