648 



GEOLOGICAL SURVEY OF THE TEEKITOEIES. 



His elevation of Saint Louis directrix above H. W. Cairo is 82.9 feet. 

 By connecting the 111. Cent, with the St. L. V. & T. H. R. E. at Van- 

 dalia, my result for the difference of elevation of these points is 96.6 

 feet; by 111. Cent. E. R. to Decatur, and T. W. & W. E. E. to Saint 

 Louis, 96 feet; by 111. Cent, to Efangham aud St. L. V. & T. H. E. E. 

 to Saint Louis, 98.2 feet; by C. & V. and St. L. & S. E. E. E.s, 93.4 feet; 

 and by a preliminary survey for railroad from Saiut Louis to Ca ro, 102 

 feet. The mean of my four determinations by constructed lines, the 

 preliminary-survey result of 102 feet being excluded, is 96.05 feet for 

 the elevation of Saint Louis directrix above H. W. at Cairo. 



I hope the evidence that I have presented will be considered as war- 

 ranting this important change of 23.3 feet that I have made in the ele- 

 vation of Saint Louis and the fall of the Mississippi Eiver.* 



ELEVATION OE OMAHA. 



- 



Eeet. 



Various datum planes. 



Elevation in feet 

 above mean sur- 

 face of Atlantic 

 Ocean. 



First determination. 



Dubuque, Mississippi Kiver, by a report from Mr. J. 



A. Lapliam, Milwaukee. 

 Dubuque, L. W. Mississippi Eiver, by Galena & Chi. 



E,Ii. 



10.00 

 13.00 

 12.00 



Above Lake Michigan 





do 





do 









589. 15 









601. 15 



Sioux City, track on levee, by 111. Cent. E. E., Iowa di- 

 vision. 



Sioux City, track on levee 



Do 



522. 50 

 534. 20 



Above L. W. at Dubuque. . 











1, 123. 35 



Mo. Valley junction with C. & N. W. E. E., by S. C. & 

 P.E.E. 



90.6 



Below S. C. track on levee. 





1, 032. 75 



Council Bluffs station, by C. Sz.'N. W. E. E 



20.00 









1, 012. 75 





31.00 







Do 





1, 001. 75 



Council Bluffs, Missouri Eiver L. W.. by two other 



reports of C. & N. W. E. E. 

 Council Bluffs, L. W. Missouri Eiver 



31.00 









1, GDI. 75 



Chech upon first determination. 



Fr6mont, by S. C. & P. E. E 



Er6mont 



190.3 









1, 223. 05 



Omaha, L. W. mark base of U. P., bv U. P. E. E 



236. 00 



Below Er6mont 





Do : 





987. 05 











This latter result is evidently the correct one ; for if L. W. was only 

 11 feet below the Council Bluffs station, as is reported by the C. & N. 

 W. E. R., then their station would be overflowed 8 feet in time of high 

 water. By the careful leveling of the bridge-company at Omaha, the 

 flat alluvial regions on both sides of the Missouri Eiver were shown to 

 be about twenty feet above L. W. Hence, I reject the report of low 

 water by tbe C. & IST. W. E. E., and by levels from Council Bluffs sta- 

 tion across to the U. P. E. E. L. W. base at Omaha. The various old 

 and new datums on the Council Bluffs side of the river cannot differ 

 over 2 feet in height. 



* Since the above was written, I liave found a report of the Saint Louis and Iron 

 Mt. E. R. surveys, signed by J. H. Morley, chief engineer, giving H. W. in Mississippi 

 River, at Ohio City, opposite Cairo, as 97 feet below the Saint Louis directrix, and 

 H. W., Mississippi Kiver, New Madrid, as 126 feet below Saint Louis directrix. 



i 



