12 Proceedings of the Royal Society of Victoria. 



Table V. 



Hence, according to Clairaut's theorem the vibration number 

 recently obtained for Sydney is too large as compared with that 

 for Melbourne, and too small as compared with that for 

 Greenwich ; while the observed vibration number for Melbourne 

 departs even more widely from that for Greenwich, being nearly 

 four vibrations less than the formula would allow. Unless the 

 pendulums have undei'gone some serious change in the course of 

 the voyage out, such change being nearly reversed during the 

 voyage to Sydney — a very unlikely concatenation of events — the 

 conclusion to which the figures lead is a defect of gravity at 

 INIelbourne, and a similar but much smaller defect at Sydney, as 

 compared with Greenwich. Setting aside any possible difference 

 between the observed and calculated values due to the difference 

 in longitude between Greenwich and the Australian stations,* 

 we may observe that this result was exactly what we might 

 expect. Melbourne being situated forty miles from the open 

 ocean, and about 250 from the deep water marked by the 200 

 fathom line, is much more of a continental station than Sydney, 

 which is near to the Pacific coast, and on a line with most of it, 

 the 200 fathom line being here within a few miles of the shore ; 

 (xreenwich, again, is on an island. The general result of pendu- 

 lum work is to show that proximity to the ocean in continental 

 stations raises the value of g for any given latitude, while an 



* We know the figure of tlie Earth with sufficient accuracy to affirm that any effect 

 arising from difference of longitude must be extremely small. 



