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



The limits of ibis J)aper and the great number of events which 

 are reviewed prevent an extensive discussion of the local evi- 

 dence, which may be found in large part in other publications. 1 

 The conclusions, however, depart from those previously ex- 

 pressed in a number of particulars, wherein studies of the field 

 or theoretical considerations have led the present writer to other 

 views. Since the subject deals with a graphic visualization of 

 the past, it lends itself to popular treatment, and technical writ- 

 ing has therefore been avoided as much as possible even at the 

 cost of some expansion in length. It should be added that the 

 structure sections here presented are wholly new, and it is hoped 

 that they and parts of the discussion may be not without interest 

 to geological specialists. 



Geologic History expressed by Structure Sections. Geologic 

 studies commonly center in a written description, and are illus- 

 trated by maps and structure sections which show the rock 

 formations as they exist at the present time. In this article the 

 form of presentation is reversed, and the later geologic history 

 of central Connecticut is made to center about a succession of 

 graphic portrayals, with written descriptions to precede and ex- 

 plain these views. A structure section passing east and west near 

 Meriden and Middletown shows the rock formations as they 

 would appear on the walls of a deep trench, and the surface 

 outline shows the magnitude and relations of hills and valleys. 

 Upon this structure section, as upon a wide canvas, the spectator 

 may in imagination review the changes which have passed from 

 age to age over this one portion of the earth. 



The structure section of Present Geologic Time, as shown 

 in Figures I and 2, is based upon the location of surface out- 

 crops, and the information which these give to the geologist con- 

 cerning the underground structure. But, except for the surface 

 line, this, like other structure sections, is the product of the 

 scientific imagination. The deeper the section is carried and the 

 more complicated the geology, the more it must fail of accuracy, 



1 See especially Davis, W. M., The Triassic Formation of Connecticut. 18th 

 Ann. Rpt. U. S. Geol. Surv., Part ii, pp. 9-192, 1898. Also, Rice, W. N., and Greg- 

 ory, H. E., Manual of the Geology of Connecticut, Bull. No. 6, Conn. Geological 

 and Natural History Survey, 1906. For geologic studies of the same formations 

 in Massachusetts see especially Emerson, B. K., Holyoke Folio, No. 50, U. S. Geol. 

 Surv., 1898. 



