OX A QUARTZ THKEAD GRAVITY BALANCE. 



to Sydney that the observations would not be of high value, but they afforded us 

 some evidence that the instrument could be transported under actual conditions 

 without serious derangement. 



The removal of the frame connecting the two axles leaves one-half of the thread 

 with a constant twist, while the other half has during each observation a slightly 

 variable amount of twist depending on the temperature and the intensity of the 

 gravitational force. Any change of gravitational force has now to be compensated by 

 a change in the twist of one-half of the thread, consequently the vernier arm has 







1'lot 4. 



Octottr 



Hoirember 



Readings reduced to 25 C. 



now to be moved through twice the angle necessary with the former arrangement ; 

 the reading-sensitiveness of the instrument was, in fact, doubled by this change. 



A gravitational survey, connecting the towns of the eastern Queensland seaboard 

 \\ itli Sydney, was now projected, the first connecting station chosen being Armidale, a 

 town on the table-land in the northern part of New South Wales. The observations 

 in Plot 3 show an immense improvement in the behaviour of the balance, 

 they give evidence of a break of 5 sextant minutes in the reading on 

 ivtuniinjj to Sydney due to the shaking which the instrument had experienced in 

 transport. We had, by this time, found out the necessity of observing only when the 

 temperature was at a maximum <>r ;i minimum. 



On the return from Armidale it was found that some air had leaked into the 

 insti iiinriit. In trying to div-'Vcr the leak, through carelessness, the delicate 



