34 CONNECTICUT GEOL. AND NAT. HIST. SURVEY. [Bull. 



lying rock, so that materials of internal and of external origin 

 were mixed in an intricate metamorphic complex. 



Probably at certain stages of the igneous activity broad floods 

 of lava, ashes, and coarse fragmental material were poured out, 

 damming and crowding aside the rivers of the time. Volcanoes 

 may have risen in places cones of igneous materials built over 

 centralized safety-valves. Such surface rocks, if they once 

 existed, have been wholly eroded from Connecticut, though still 

 preserved in eastern New England. In Connecticut they must 

 therefore be restored with a bold hand on the basis of the subter- 

 ranean evidence now exposed. But over the Lowland even this is 

 hidden by the Triassic rocks, and the structure section shows 

 merely the kind of landscape which may have prevailed in 

 Connecticut at the close of the Paleozoic. 



Recently conglomerates of late Paleozoic age which occur near 

 Boston have been found to contain glacial deposits, but it is not 

 probable that the late Paleozoic glaciers of the Appalachians 

 reached an extent comparable to the ice sheets of the last or 

 Quaternary glaciation of North America. The late Paleozoic 

 glaciation of the southern hemisphere, the fragmentary evidence 

 of which is now buried in the solid rocks, was, however, the most 

 widespread known in earth history, and was developed apparently 

 without relation to present climatic zones, occurring in South 

 Africa, India, Australia, and South America. The regional 

 climate in New England at the time is thought therefore to have 

 approached a glacial climate. This cold and humid condition it 

 has been sought to shadow forth in the cloud forms which have 

 been drawn across the landscape: 



This final view has penetrated through only the last fraction 

 of geologic time, but already for central Connecticut the vision 

 fails, and, like these lowering clouds, the obscurity of the past 

 hides all which lies beyond. 



THE PANORAMA OF GEOLOGIC TIME. 



The preceding pages have presented a summary of the evidence 

 upon which the restorations of the successive periods have been 

 based, passing from the present and the known to the past and 

 the unknown. The study has carried us into the close of the 

 Paleozoic. From this turning point in earth history which marks 



