SOURCE OP ST. Peter's river. 203 



we had passed that day, without stopping, were probably 

 also remains of the general sandstone formation which ex- 

 tended over the whole country. No organic remains were 

 observed in the sandstone, or in the limestone which under- 

 lays it ; but no doubt can exist that they may contain some, 

 and that the limestone probably contains many. 



Proceeding towards the Wisconsan, the country pre- 

 sents an alternation of rolling and undulated prairie, inter- 

 spersed with hills composed of either one or the other of 

 these rocks. The sandstone is found in most places to be 

 covered with thin flattened fragments of a stone, differing 

 in its nature and texture from the character of the other 

 rocks, whether of limestone or sandstone. These frag- 

 ments are generally observed to vary from three to twelve 

 inches in length, from two to eight in breadth, and from 

 one quarter to one inch in thickness ; they present appear- 

 ances of having been weathered, but not of having been roll- 

 ed ; they arc veiy abundant, and we could account for them 

 in no other way than by admitting that they were the re- 

 mains, probably the harder parts, of a stratum that had at 

 one time covered the sandstone, but that had disappeared 

 almost entirely, leaving only these fragments to attest its 

 former existence and situation. On examining these frag- 

 ments with care, we found them to be very uniform in their 

 characters ; their composition is in great measure calcareous, 

 but from their greater hardness we coTisider it as partly silice- 

 ous ; they are replete with organic remains ; these are princi- 

 pally referrible to the Productus, Terebratula, &c. We saw 

 none but what belonged to bivalves. The existence of 

 these fragments was observed upon many elevations, over 

 a considerable extent of country, while in the vallies no 

 trace of them could be seen. Generalizing the observa- 

 tions made during the three last days of our journey pre- 



