GAEDNER.] 



GEOGEAPHT ELEVATION OF DATUM-POINTS. 



633 



sidered that the line of levels from the Atlantic to Ogden, Utah, is about 

 two thousand miles lon.a:, this discrepancy is small. It is not improba- 

 ble that a large part of this error lies between Cheyenne and Ogden, 

 where the work on the U. P. E. E. was driven at an unprecedented 

 speed, and where the line lies over mountains. The accompanying map 

 shows the lines of levels that have entered into this discussion. 



J^isciission of evidence of tJie altitudes of various xjoints in the United 



states and Canada. 



THE ELEVATIOIf OE LAKE ONTAEIO. 



First determination. 



tean tide at Albany, by XTniteil States Coast Survey 

 I leveling. 



ean surface of Lake Ontario, by report of final level- 

 ings of Erie Canal, (see profiles accompanyinff an- 

 nual report of State engineer and surveyor of "ifew 

 i York, January 1, ltC8, by J. P. Goodsell.) 

 ilean surface of Lake Ontario 



Second determination. 



pan tide in St. Lawrence Eiver at Three Kivers, 

 datum of levels of G. T. E, W. of Canada. 



surface of Lake Ontario. 



Do 



[These figures are from a report of the chief engineer 

 of the G. T. E. W. of Canada, dated M.irch, 1872.) 

 lean high-tide at Portland, Me., by United States Coast 

 Survey report. 



Surface of Lake Ontario 



Final results. 



Surface of Lake Ontario : 



First determination 



Second determination , 



Adopted as correct 



Error of second determination 



Feet. 



6.77 



235. 00 

 241. 77 



4.5 



Various datum-planes. 



Above mean tide west 

 end of Eighteenth 

 street, Kew York. 



Above M. T., Albany . .. 



Above M. H. T., at Port- 

 laud, Me. 



Above M. T., Three 



Kivers. 

 Above M.H.T., Portland 



Above M. T., Portland. 



.2 o o o 



4.84 



249. 99 



246. 27 



249. 99 

 246. 27 

 249. 99 



The first determiuatiou is adopted, because it is the final result of 

 many years' leveling over the line of the Erie Canal, as against the result 

 of a long and broken line of railroad-levels 5 aud because the canal-engi- 

 neers have undoubtedly taken greater pains to get the mean surface of 

 the lake than the railroad-engineers, to whom such knowledge was of 

 110 practical importance. 



At Montreal, the levels of the G. T. E. W. are checked approximately 

 by levels run by the Montreal and Champlain E. E. Co., Montreal, sum- 

 mer, water in river is 30 feet above mean sea by the G. T. E. W. ; by 

 the M. & C. levels L. W. at Montreal is 69.7 feet below L. W. Champlain. 

 The surface of the lake is 100.84 feet by canal from Albany ; hence L. 

 VV. Montreal about 31 feet. Considered with reference to Lake Cham- 

 plain, we have its height above mean sea 100.84 feet by Hudson Eiver and 

 Whitehall Canal, and 99.7 feet by G. T. E. W. from Portland. 



