Chap. 7] 



GRAVITATIONAL METHODS 



271 



himselfj was the first to realize the merit of lake measurements. Even 

 before he had developed his double gradient and curvature variometer, 

 he surveyed thirty-tliree stations on the ice of Balaton Lake in 1901 and 

 twelve stations in 1903. Similar measurements were made in 1924 by 

 Hoist *^^ in the Black Forest on Lake Titi. This lake is of glacial origin. 

 Its greatest depth is 39 meters, and the bottom formation is gneiss covered 



Fig. 7-103a. Bottom contours (in decimeters) of Lake Shuvalovo (after Numerov). 



by a thin layer of morainal material. The observed torsion balance 

 anomalies were large because of the large density difference between water 

 and rock (1.7). Since the lake profile was well known from soundings, the 

 observed indications could be compared with theoretical anomalies (calcu- 

 lated by means of the slope formula [7-93c]). 



^" R. V. Eotvos, Result, wiss. Erforsch. Balatonsees, Vol. I, Geophys. Appendix 

 (1908). 



»8 E. Hoist, Zeit. Geophys., 1, 228-237 (1924-1925). 



