REPORTS OF RESEARCH COMMITTEES. 295 



The observations have been systematically carried out by the 

 same observer. Mr. A. Goodwiu, since the pendulums were first 

 established. This has, of course, been a matter of great import- 

 ance for the success of the investigation, as Mr. Goodwin has be- 

 come most proficient in the care of the instruments, and has been 

 able to make many useful, practical suggestions for improving the 

 quality of the records. Mr Campbell, the engineer in charge at 

 Burrinjuck, has personall}'- taken a great interest in the work, and 

 has, with his technical experience, been able to overcome manv 

 mechanical difficulties arising from the defective working of the 

 registering apparatus. The writer has visited the instrument at 

 intervals of from three to six months, has taken the periods of 

 the penduhims, and has kept them in proper working adjustment. 



At the time when the instruments were first installed it was 

 the intention of the Government to have completed the building 

 of the dam in about three years. The outbreak of war, however, 

 modified their plans, and the work was largely suspended. As 

 the consequence of this delay the full storage capacity of the dam 

 at present is only about one-half of that which will be available 

 when the work is completed. The work will probably not be com- 

 pleted for another two years. It is, of course, most desirable that 

 the pendulums should be in operation when the full water-load 

 is impounded. The Irrigation Commission has been most generous 

 in its help, and. although the investigation has been much pro- 

 tracted, is still rendering all the assistance necessary for making 

 a success of the work. 



The records obtained during the period of the war have not 

 been as complete as would have been desirable, but this was 

 inevitable, as the supplies of standard photographic paper could 

 not be constantly depended upon, and the records suffered in con- 

 sequence. On the whole, however, the records are satisfactory, but 

 the records cf the next two years should be the most valuable of all. 



The examination of the records made since the publication of 

 the preliminary note in December, 1915. have served to explain 

 in large measure the movement which was then regarded as being 

 secular in character. It now appears that the movement is chiefly, 

 if not wholly, seasonal in character, and that it is a function of 

 the underground temperature. 



This was first noticed by Mr. Campbell, -who drew my attention 

 to the similarity of the pendulum displacements and the tempera- 

 ture variations registered by a thermometer within the concrete 

 dam at a distance of about 80 feet from, the surface. The tem- 

 perature curve of this thermometer lags some months behind the 

 ordinary atmospheric temperature curve, and the pendulums 

 exhibit the same kind of lag in their movements. 



