SOURCE or ST. Peter's river. 183 



these do not appear to be so frequent here, whether it be 

 because they are buried in, and concealed by the pebbles, 

 or because they were not deposited here, we had no 

 means of determining. The alluvion appears to consist 

 chiefly of the detritus of primitive rocks, such as fragments 

 of quartz, granite, sienite, &c. but, as far as we could observe, 

 without any trace of a metalliferous mineral. There are 

 also many fragments of limestone, interspersed throughout 

 the mass. Under the alluvion, the limestone observed in 

 the morning probably extends to a great distance. From 

 the observations which we have been able to make, we 

 believe it to be the same limestone formation, which extends 

 from Piqua to Fort St. Mary, and which is seen near 

 Fort Wayne, Chicago, and Rock river. Whether it be the 

 same as that observed further east, or in what relation it 

 stands to it, we are not desirous of deciding positively, but 

 we believe it to be at least as modern as that found above 

 the coal formations of Wheeling and Zanesville, and per- 

 haps more so. We have spoken of the supposed lead for- 

 mations of Rock river; not having visited Dubuque's lead 

 mines, or those in the state of Missouri, it would be impos- 

 sible for us to express a decided opinion upon their nature ; 

 but from all that we have heard on the subject, as well as from 

 what has been written upon these lead mines, we can 

 scarcely hesitate in considering the ore as being equally 

 out of place there. Whether the original sites, from which 

 it has been detached, are still to be found in the vicinity, 

 is a point which those alone who have seen the country 

 are competent to decide, if indeed the question can in the 

 present state of science be resolved ; the authors who have 

 written upon this subject have, as it appears to us, left the 

 question open ; for while they assert that the lead is found 

 in clay, they appear to us desirous to convey, at all times. 



