612 



SEISMIC METHODS 



[Chap. 9 



Dfttctir Amplifier 



Fig. 9-116. Condenser seismograph. 



Conn* 



(a) 



Fig. 9-117. Ambronn accelerometer-refraction sesimograph (partly after Sifieriz). 



ments a compensated-spring-type vertical seismometer was developed, 

 which resembles in construction the La Coste instrument. 



68 L. J. B. La Coste, Physics, 6, 178 (1934); and Seis. Soc. Amer. Bull., 26(2), 176 

 (1935). 



