94 E, F. J. Love : 



for Melbourne and Sj^dney we obtain, in terms of the Helmert geoid 

 of 1901, viz.: — 



yjj^-978-030 (1 +0 005302sin2<^ -0-000007sin22<^), 



for Melbourne: (^o = 979-99o, 9/ = 979992, 7^ = 979 974, 



</o" - 7o = + -01^. 9o-yo=+ -^^i 



for Sytlney: ^o = ^79693, gf^''^ 979689, yo = i^79-63'l, 

 9o' -7,,= +-055, 5f^ - y^ := + -059 



In terms of the Helmert geoid of 1915, in which the ellipticity 

 of the equator and parallels first makes its appearance (and that 

 with a somewhat surprisingly large coefficient for the longitude term) 

 I find that both anomalies are much smaller. The equation of the 

 .new geoid is: — 



y^= 978 • 052 [1 + • 005285sin2 (^ - • 000007sin22<^ 

 ±3 +5 



+ • 000018cos2<^cos2 (^x + 17 ) ] 



where x denotes the longitude, reckoned positive when E. of Green- 

 wich. Hence we obtain: — 



for Melbourne : yo =979*999, g^" - yo = - "007, gQ-y^= - 004, 

 for Sydney : y^ = 979-662, g^" - yo = + '027, ^^ - To = + ■<^31. 



The negative sign of these anomalies for Melbourne is noteworthy. 

 Melbourne is, to all intent, an inland station in an extended region 

 of low topograhic relief; n for it, therefore, the free-air and isostasy 

 anomalies are not likely to differ much, and the negative sign of the 

 former may possibly be correlated with its position in a region 

 largely covered with relatively light rocks of late geological age, and, 

 where of earlier age, mainly Silurian. Sydney, being a coastal station 

 near to deep water, the correlation between its gravitational anomaly 

 and the geological age of the neighbouring surface rocks is very 

 likely to be masked by a large topographic effect, of which the 

 Bouguer and free-air reductions fail to take account; a fresh reduc- 

 tion by the Hayford-Bowie metliod might clear up this point. 



The anomalies, g " -y and g —y for Brisbane and Hobart, In 

 ' ' 



terms of Helmert's 1901 geoid, are given by Borrass (I.e.). Those for 



Perth, 12 together with the anomalies for all three stations in terms 



of the 1915 geoid, are as follows: — 



1901 geoid. Perth: j?o=979-392, jr/' = 979-387, yo = 979-477, 



Sfo"- 70 =--090. .90-70 =--085* 

 1915 geoid, Perth: yo = 979493, g^" -y^^^ --106, gro-7o= - "lOl. 

 Brisbane: y^, =979-160, j^o"" 7o= - "004, g^, - 7o = -^0- 

 Hobart : yo = 980*446, fiTy" - yo = + *007, </„ - y^ = + -013. 

 The asterisked figure is also given by Alessio. 



11. Port Phillip, geodetically speaking, is a shallow lake. 



12. See Appenidix 4. 



