SOURCE OP ST. Peter's river. 167 



object, would again render Lake Michigan a tributary of 

 the Mexican gulf. Impressed with the importance of this 

 object, the legislature of Illinois has already caused some 

 observations to be made upon the possibility of establishing 

 this communication ; the commissioners appointed to that 

 effect, visited Chicago after we left it, and we know not 

 what results they obtained, as their report has not reached 

 us ; but we have beerrinformed that they had considered 

 the elevation of the petit lac above Chicago to be some- 

 what greater than we had estimated it. It is the opinion 

 of those best acquainted with the nature of the country, 

 that the easiest communication would be between the Lit- 

 tle Calamick and some point of the Des Plaines, probably 

 below the Portage road ; between these two points there 

 is in wet seasons, we understand, a water communication of 

 ten or twelve miles. Of the practicability of the work, and 

 of the sufficiency of a supply of water no doubt can exist. 

 The only difficulty will, we apprehend, be in keeping the 

 communication open after it is once made, as the soil is 

 swampy, and probably will require particular care to op- 

 pose the return of the soft mud into the excavations. 



In the immediate vicinity of Chicago, a secondary lime- 

 stone is found, disposed in horizontal strata ; it contains many 

 organic remains. This limestone appears to us to be very 

 similar in its geological as well as mineralogical as|>ect, to 

 that observed above the coal formation on the Miami ; but 

 no superposition being visible, it is impossible for us to 

 determine at present its relative age ; we however incline 

 to the opinion, that it is one of the late secondary lime- 

 stones. We have to regret that the specimens which were 

 obtained of the same have been lost, and that we are depriv- 

 ed of the opportunity of comparing them with those col- 

 lected in other parts of our route. This limestone, which 



