32 PHYSICAL GEOGRAPHY. 



-westward from Cass county was constructed from data furnished from the Geo- 

 logical Survey notes, and by estimating the elevations from known slopes of 

 rivers and watersheds. 



Profile No. 5. 1 he elevations on the line of this profile from Burlington to 

 Highland in Union county, (the highest point on the line between the two great 

 rivers) are those of the Burlington and Missouri River Railroad. Westward 

 from Highland, there being a discrepancy of from fifty to seventy feet between 

 the elevations as given by that railroad and those obtained from other sources, 

 and which may be connected with the same terminus, the elevations given in the 

 profile are somewhat raised to correspond with those other data, all of which 

 point to higher elevations than those of that part of the Burlington and Missouri 

 River Railroad levelings. 



Regarding other work, with the data furnished by the railroad engineers and 

 obtained from other sources, there has been some difficulty in correcting the 

 levels and reducing them all to the same datum, owing to the fact that in the 

 majority of cases where two different lines intersect, but one gives the elevation 

 of that particular point, thereby rendering it somewhat difficult to determine the 

 exact difference of data. In some cases, however, both lines have given their 

 elevations at the point of intersection. In such cases the results are generally 

 satisfactory. We have Nicollet's elevations along the Mississippi river with 

 which we are able to compare the lines of railroad levelings at their outset, and 

 where it has been possible to test the accuracy of his determinations, the error, if 

 any, has generally been found to be small. 



The differences from a true level in the various lines of railroads across the 

 State seem to be cumulative towards the west ; or, in other words, the farther 

 they are extended in that direction from their starting point, the greater the error 

 from a true level; so that we may expect greater error in the elevations as given 

 in the vicinity of the Missouri river than in those nearer the Mississippi. When 

 authorities differ as to the elevation of any point, if the difference is slight I have 

 taken the mean. If the differences were considerable I have adopted those 

 which seemed most authentic and fully corroborated. On the whole, however, 

 the elevations given have all a degree of accuracy that reflects great credit upon 

 all the engineers concerned in their determination, and the results will give a 

 good general idea of the topography of the State." 



Since, with few exceptions, the different railroad levelings 

 show the actual position of the road-bed, and since those 

 roads necessarily follow the valleys of streams as far as 

 practicable, for the purpose of securing an easy grade, 

 profiles drawn from their data alone would not present an 

 outline exactly corresponding to the general contour of 

 surface along independent lines across the State. Therefore 

 a dotted line has been added to each of those profiles for the 



