ACCURACY OF DETERMINATION OF RELATIVE 
GRAVITY BY TORSION BALANCE! 

DONALD C. BARTON? 
Houston, Texas 
ABSTRACT 
Determination of relative gravity by the Eétvds torsion balance has been shown by 
Oltay and others to be as accurate as the determination by the invariable pendulum. 
In the present paper, the probable error of the torsion balance determination of rela- 
tive gravity is calculated from the error of closure of 45 traverses comprising 2,800 
stations, most of them in the Gulf Coast region. The probable error of each individual 
observation in those surveys is calculated to have been +2.2 Eétvés units for the 
traverses taken together, or from +1.9 E for the traverses with the larger station 
interval to +5 F for the traverses for the small station interval. But the greater error 
of the individual observations in the traverses which have the shorter station interval 
has been compensated, intentionally, by that shorter interval, and the probable error 
of the determination of relative gravity by those 45 traverses is approximately 0.4 
milledyne per 10 kilometers of traverse without regard to the magnitude of the probable 
error of the individual observations or of the station interval. The probable error of the 
determination of relative gravity between key points in good torsion balance surveys 
presumably is approximately + 2.5 to +2.5 E per 10 kilometers airline distance between 
the two places. If pendulum determinations of relative gravity are used to supplement 
and to increase the accuracy of torsion balance surveys, there is a minimum interval 
at which the pendulum stations should be placed, for at lesser intervals the determina- 
tion of relative gravity by the torsion balance is more accurate than that by the pendu- 
lum. That minimum interval ranges from 100 to 200 kilometers for the pendulum ob- 
servations of the first quarter of the century to 8 to 50 kilometers for first class modern 
pendulum observations. 
The relative accuracy of the determination of relative gravity by 
good torsion balance surveys in favorable terrane has been shown 
by Oltay, Jung, Numerov, and others to be comparable with the 
accuracy of the determination of relative gravity by the invariable 
pendulum during the past quarter century. The differences between 
the relative gravity by the torsion balance and pendulum on six 
traverses in the Arad district of the Hungarian plain were respectively 
0.001, 0.001, 0.004, 0.000, 0.005, 0.000 cm. sec.” The respective 
lengths of the traverses were 12, 9, 13, 20, 42, and so kilometers.? 
The probable error of the pendulum observations was calculated to 
1 Read before the Association at the Oklahoma City meeting, March 25, 1932. 
2 Consulting geologist and geophysicist, Petroleum Building. 
* Karl Oltay, “Die Genauigkeit der mit der Eétvésschen Drehwage Durchge- 
fuhrten Relativen Schwerkrafts-messungen,” Geoddtische Arbeiten d. Baron R. v. 
Eotvisschen Geophysischen Forschungen, No. III (Budapest, 1928). 
65 
