640 GEOLOGICAL SURVEY OF THE TEEEITOEIES. 



From mean tide New YorTc Bay to tlie Chicago directrix. 



• 



Feet. 



Various datum-planes. 



Elevation in feet 

 above mean sur- 

 face of Atlantic 

 Ocean. 



By the N. Y. C. R. ~R. : 



Mean tide Albany, by TTnited States Coast Survey. 



4.84 



578. 23 



17. 30 



12. 80 



Above M. T. New York . . 





JBufl'alo depot, by N.Y.G.B.K 



Chicago depot, ty L. S. & M. S. K. R 









. . .. 



Below Chicago, L. S. &. M. 

 S. depot. 





Do 



587. 57 



Total distance frona New York Bay, 980 miles. 

 By the Pa. E. E. : 



6.913 



738. 00 



151.00 



8.50 



Above M. T. Earitan Bay. 





Pittsburgh Union clepot, by Pa. E. E '. . . 



Chicago depot, by P. P. W. & C. E. E 

















585. 41 



Total distance, about 900 miles. 



Chicago dii-ectrix, by N. Y. C. & L. S. & M. S. E. E., 980 



miles. 

 Chicago directrix, by Pa. E. E. & P. F. W. & C. E. E., 



900 miles. 



587. 57 



585. 41 



2.16 



Above M. T. New York 





Above M. T. Earitan Bay. 











These lines are about one hundred and fifty miles apart tbrougli 

 tlie first half of their course and about fifty miles in the western part. 

 The Pa. E. R. crosses the Appalachian-mountain system in a difficult 

 place, rising to a height of 2,290 feet, among ridges that must exert con- 

 siderable attraction upon the level, while the ]N", Y. C. and L. S. & M. 

 S. Eailroads are through comparatively level country; and yet, after 

 this long course of about nine hundred miles, they reach Chicago with 

 only two feet difference in their levels. The result seems truly remark- 

 able. The height by the Pa, E. E. differs — 1.74 feet, and by the K' Y. 

 C, L. S. & M. S. E. E. +0.42 feet from the adopted elevation. 



The N. Y. C. E. E. is checked at Buffalo, three hundred miles from 

 Albany, by a connection with surface of Lake Erie, state of water un- 

 known, but assumed to be mean surface. The railroad-levels are 0.7 foot 

 too high. At Cleveland, four hundred and eighty miles from Albany, 

 the railroad-levels are 0.41 feet too high, and at Chicago 0.42 feet too 

 high. The Pa. E. E. is checked at Harrisburgh, one hundred miles from 

 Philadelphia, where it is intersected by the IST. C. E. E., bringing its 

 levels from mean tide at Baltimore, eighty-four miles. The two lines of 

 levels differ but 0.16 feet. It is checked again at Pittsburgh, three hun- 

 dred and fifty miles from Philadelphia, where the B. & O. E. E. inter- 

 sects, bringing its levels from mean tide at Baltimore about three hundred 

 miles. The levels by the Pa. E. E. are 2.16 feet higher than by the .B. & O. 

 E. E., but the connection of the i^rofiles of the two is not exactly certain. 

 It is, however, not improbable that mean tide at Baltimore is a little 

 above the mean level of the ocean. At Alliance, the P. F. W. & C, the 

 -extension of the Pa. E. E. line of levels to Chicago, is checked by the 

 C. & P. E. E. from the Cleveland directrix. The elevation of Alliance 

 by the Pa. E. E. and P. F. W. & C. E. E. is 1081.61 feet; that by the 

 C. & P. E. E. is 1083.23 feet ; the P. F. W. & C. being probably too 

 low. 



At Crestline it is checked again from the Cleveland directrix, the ele- 

 vatiou by the P. F. W. & C. E. E. being 1152.51, and that by the C. 



