CONNECTICUT RIVER SANDSTONE. 27 



since their deposition, and their original level positions transformed into various 

 angles of elevation. The fossil-bearing strata present smooth, lustrous surfaces, — 

 a condition that results from the precipitation upon the coarser materials of the 

 strata of such fine argillaceous particles as were held in suspension by the agitated 

 waters; and upon this polished film, when exposed by the retreating flood, the 

 animals impressed their footsteps as upon wax. The plastic and retentive proper- 

 ties of this sedimentary deposit were very remarkable, the minutest details of 

 organization being engraved upon it sharp as the impress of a die. 



When several contiguous strata are impressed with footprints, each succeeding 

 stratum bears upon its inferior surface an exact copy of the stratum beneath ; 

 and hence it happens that certain strata bear intagliated impressions upon their 

 superior, and relievo casts upon their inferior, surfaces. When a new layer over- 

 spreads a preceding deposit, an interval of quiet and sunshine succeeded ; by 

 parting with its water its surface became consolidated, and in this condition the 

 animals imparted to it the impress of their feet, which has been preserved 

 unchanged by the succeeding overflow of plastic mud, and thus the process con- 

 tinued indefinitely, each stratum not only taking the form of its predecessor, but 

 preserving its records from destruction. 



The original deposition of the sandstone beds covered an area of considerable 

 length, but of limited breadth. Its present northern terminus is at a cataract 

 in the Connecticut River known as Miller's Falls, near the northern boundary 

 of Massachusetts, and, stretching to the south, it intersects this State and also 

 that of Connecticut. The Connecticut River proceeds, in its southern course, 

 directly over the sandstone beds, as far as Middletown, in the latter State, and 

 is thence diverted to the east, over beds of metamorphic rocks, the sandstone 

 continuing in its straight course, and terminating at the Long Island Sound, at 

 New Haven. Footprints usually occur wherever the stratified division of the 

 rock is extensively quarried, as at Middletown and Weathersfield in Connecticut; 

 and at Chicopee, South Hadley Falls, and Turner's Falls, and at other localities 

 in Massachusetts. The localities are numerous, and are distributed over an extent 

 of more than one hundred miles. The facilities for investigation are in pro- 

 portion to the elevation of the original beds; but footprints do not occur in all 

 situations in the same degree of perfection. At the cataracts of Turner's Falls 

 they are riot only most abundant, but of extraordinary excellence. Their superi- 

 ority perfectly adapts them to the purposes of illustration, and the originals of 



