ABSTRACTS 



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GEODESY. — -Precise leveling from Brigham, Utah, to San Francisco, 

 Cal. William Bowie. U. S. Coast and Geodetic Survey. Spe- 

 cial Publication No. 22. Pp. 67. 1914. 

 This publication gives the results of a line of precise levels run along 

 the Southern Pacific Railway, from Brigham, Utah, to San Francisco, 

 California, in 1911 and 1912. The line is 891 miles long and fixes the 

 elevations of 315 permanent bench marks. The elevation of the top of 

 rail in front of each of the railway stations along the line was also de- 

 termined. The elevations of the bench marks and of the top of rail 

 in front of the railway stations are given in meters and feet. As in all 

 precise leveling in the United States the datum used is mean sea level. 

 This line was fitted or adjusted to the elevations resulting from the 

 1912 adjustment of the precise level net of the country (Special Publi- 

 cation No. 18), hence the elevations given are standard, that is, they 

 will not be changed as the net is further extended. Included in this 

 report are discussions of the methods used and the accuracy attained 

 in precise leveling. 



The result of a study of the errors of leveling is also reported on. 

 The basis for this study is the data for five level lines, giving the times 

 of the runnings of the different sections, with the weather conditions 

 prevailing at the time the observations were made. The data are ar- 

 ranged in eight tables in such a manner as to set forth various relations 

 between the errors of leveling and the conditions of weather, the time 

 of the observations and the grade. It is believed that, other things 

 being equal, the running in the afternoon gives, on an average, more 

 accurate results than the forenoon leveling; also that, other things be- 

 ing equal, a running in wind is more accurate, on an average, than one 

 in calm; and that, other things being equal, a running with a cloudy 



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