450 L. A. COTTON. 



proper installation. It was decided that if possible they 

 should be placed in tunnels in the steep hillsides as close 

 as practicable to the high water level of the Burrinjuck 

 reservoir. The steep slope of the hills (about 30°) would 

 enable the instruments to be established at a sufficient 

 depth from the surface to minimise or eliminate the effect 

 of surface temperature changes. The State Government 

 generously granted the aid necessary to the preparation of 

 these tunnels. The greatest thanks are due to the late 

 Commissioner for Irrigation, Mr. L. A. B. Wade, for his 

 personal interest and help in connection with this work, 

 and also to Mr. Dare, the present Acting Commissioner, at 

 that time Chief Engineer to the Irrigation Commission. 

 The tunnels were driven under the supervision of the 

 resident engineer at Burrinjuck, Mr. D. P. Campbell. This 

 gentleman has rendered the most invaluable service both 

 in connection with the installation and the subsequent 

 maintenance of the instruments. It is due to his enthusi- 

 astic devotion and interest, that in spite of many difficulties, 

 the records of the present year have yielded such satis- 

 factory results. Thanks are also due to Mr. Goodwin for 

 his valuable services in changing the records. 



The selection of the sites for the tunnels and the instal- 

 lation of the instruments were carried out jointly by Pro- 

 fessor David, Father Pigot, Mr. D. F. Campbell and the 

 writer. The sites chosen are shown on the accompanying 

 map (Plate LXII). The tunnels are placed from twenty 

 to forty feet above high water level and are from sixty to 

 eighty feet in length. Each tunnel is divided transversely 

 into three compartments. The pendulums are housed in 

 the compartment remote from the entrance, the lamp and 

 photographic recording apparatus in the centre compart- 

 ment, while the outer compartment serves as a storage 

 room for accessories and as an additional protection to the 



