SOME GEO-PHYSICAL OBSERVATIONS AT BURRINJUCK. 455 



world scheme initiated by Hecker for the International 

 Geodetic Association. It was established by Father Pigot 

 at Cobar a short time before he commenced the installation 

 at Burrinjuck. The Cobar instrument is of the Zollner 

 suspension type and was set up in a disused mining drive 

 at a depth of 450 feet from the surface. As Cobar is about 

 360 miles from the coast it is anticipated that the effect of 

 the oceanic tides will be quite negligible at this station. 

 If the oceanic tides do exert a measurable effect at Burrin- 

 juck, a comparison of the records with those of Cobar should 

 provide a means of ascertaining the magitude of this effect. 

 If, on the other hand, the oceanic tides exert no appreciable 

 influence at Burrinjuck, the records will be of value in 

 supplementing those at Cobar. Unfortunately the Cobar 

 mine has been closed during the greater part of the past 

 year, so that simultaneous records from Cobar and Burrin- 

 juck are not yet available. The mine is, however, now 

 being re-opened, and the installation of the pendulum will 

 be shortly re-established by Father Pigot. 



Earthquakes are readily recorded by all the pendulums. 

 The periods of the booms in the different instruments vary 

 from about eighteen to twenty-six seconds for a relatively 

 small arc of oscillation. These records have of course no 

 time value, as the travel of the photographic paper is only 

 from one to three centimetres per hour; nor are the ampli- 

 tudes of much value as the pendulums are undamped. 

 Nevertheless the earthquakes are of importance in their 

 possible relation to faulting. Earthquakes of large ampli- 

 tude have on several occasions been accompanied by sudden 

 displacements of the zero of the booms under conditions 

 which sometimes suggest fault movements rather than 

 instrumental errors. As a rule the earthquakes are not 

 accompanied by displacement of the zero position of the 

 booms. 



