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 THE LIBRARY 
 
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 THE UNIVERSITY 
 
 OF CALIFORNIA 
 
A CONNECTION BY PRECISE LEVELING BETWEEN 
 THE ATLANTIC AND PACIFIO OCEANS 
 
 BY 
 
 DR. JOHN F. jHAYFORD 
 
 [Reprinted from Science, JV^ S. , Vol. XXL , No. 5S9, 
 Pages 673-674, April 28, 1905.'] 
 
 
n ^^^^ 
 
 lEeprinted from Science, N. /S'., Vol. XXI., No. 
 539, Pages 673-674, April S8, 1905. ] 
 
 A CONNECTION BY PRECISE LEVELING BETWEEN 
 THE ATLANTIC AND PACIFIC OCEANS. 
 
 On October 4, 1904, a Coast and Geodetic 
 Survey party, running eastward from Seattle, 
 Wash., met a similar party, running westward, 
 at Hunts Junction, in the southeastern part 
 of Washington. The party running from east 
 to west had started in the beginning of the 
 season from a bench mark of which the eleva- 
 tion had been fixed by a long line run during 
 several seasons and extending westward from 
 the precise level net, composed of many cir- 
 cuits, which covers the eastern half of the 
 United States. As far west as Norfolk, Nebr., 
 the elevations in this net had been checked 
 by completed circuits of precise leveling of 
 the highest grade of accuracy. The joining 
 of the two lines at Hunts Junction completed 
 the first connection by precise leveling be- 
 tween the Atlantic and the Pacific. 
 
 The discrepancy developed at the junction 
 was .615 ft. (=187.5 millimeters), the Pacific 
 being apparently higher than the Gulf of 
 Mexico and Atlantic. 
 
 The old question at once arises: is the 
 Pacific at a different elevation from the At- 
 lantic? The discrepancy of .615 ft. must be 
 due either to errors in the tidal observations 
 which furnished the connection with mean 
 sea level, or errors in the leveling, or to a real 
 difference in the elevation of the mean sea 
 surface at the points at which the tidal ob- 
 servations were made. 
 
 The three principal connections with sea 
 level concerned are at Sandy Hook, near New 
 York City, at Biloxi, Miss., and at Seattle, 
 
Wash. Six years of tidal observations were 
 taken at Sandy Hook and five years at each 
 of the other points. The range in the six 
 annual means at Sandy Hook was .322 ft., 
 and of the five annual means at the stations 
 at Biloxi and Seattle was, respectively, .100 
 and .204 ft. These ranges are not sufficient 
 to account for the discrepancy of .615 ft. 
 
 The shortest line of leveling of the highest 
 grade of accuracy from Seattle to Sandy Hook 
 is 4,600 miles (7,400 kilometers) ; to Biloxi, 
 3,500 miles (5,700 kilometers) ; and to Norfolk, 
 the point at which the line to the westward 
 leaves the thoroughly checked portion of the 
 precise level net, is 2,000 miles (3,300 kilo- 
 meters). 
 
 If it is assumed that the discrepancy (.615 
 ft.) is simply an accumulated error in leveling 
 and that the rate of accumulation is uniform 
 between Seattle and Biloxi, it is at the rate 
 of one foot in 5,700 miles (.033 millimeters 
 per kilometer). Even if it is assumed that 
 the accumulation all occurred between Seattle 
 and Norfolk, it is at the rate of one foot in 
 3,300 miles (.057 millimeters per kilometer). 
 This is an extremely small error of leveling. 
 
 Another test to determine whether the dis- 
 crepancy is a possible error of the leveling 
 may be applied. The probable error of the 
 elevations at Seattle, as carried westward from 
 the Gulf and Atlantic, tiie computation being 
 based upon the discrepancy developed in the 
 circuits in the eastern part of the United 
 States, was db 76 millimeters. The actual dis- 
 crepancy is two and one half times this. Ac- 
 cording to the doctrine of chances, such a 
 discrepancy, two and one half times the prob- 
 able error, should occur about once in ten 
 times. 
 
 Therefore, it is not safe to make the state- 
 ment that the Pacific is higher than the Gulf 
 and Atlantic; the extremely small discrepancy 
 being well within the possible limits of error 
 of the precise leveling alone, even though it 
 
be assumed that the leveling in question is of 
 as high a grade of accuracy as any yet done 
 anywhere in the world. 
 
 One is apt to associate observations of such 
 extreme accuracy as this precise leveling with 
 slow progress and high cost. It is interesting, 
 therefore, to note that three thousand miles 
 out of the thirty-five hundred between Seattle 
 and Biloxi have been leveled since the begin- 
 ning of the field season of 1899, and that the 
 average rate of progress, during the period 
 1900-1904 (a total of 3,900 miles), with the 
 new type of precise level now in use in the 
 Coast and Geodetic Survey, was 64 miles of 
 completed line per month, for each observer, 
 and that the average cost, per completed mile, 
 was $10, including salaries, transportation 
 and bench marks. Each completed mile was 
 leveled over at least twice, and, in some cases, 
 four or more times. This rate of progress is 
 comparable with that ordinarily secured in 
 wye leveling, which is of a much lower order 
 of accuracy. John F. Hayfobd. 
 
Digitized by the Internet Archive 
 
 in 2007 with funding from 
 
 IVIicrosoft Corporation 
 
 http://www.archive.org/details/connectionbyprecOOhayfrich 
 
PAflNPHLET BINDEt 
 
 Syracuse, 
 Stockton,