TRIGONOMETRICAL SURVEY OF NEW SOUTH WALES. 183 
other surveys of similar importance of making local adjustment and 
permitting no rejections on account of apparent discordance has 
been followed, and, in the series of triangles south from the 
Lake George base to the boundary of the Colony, adjustment to 
meet the geometrical conditions of such figure has been made by 
the method of least squares. Owing to the need for attending to 
the current work of the office and to the staff available for such 
calculations being limited, none of the older work has been re- 
computed. 
ELEMENTS ADOPTED. 
Upon the writer taking charge of the computation of the 
survey some few years back it was found that the following 
dimensions for the earth had been made use of in the previous 
calculations, viz. :— 
Major semi-axis = a@ = 20,923,134 feet. 
Polar 35 = Cr 20 Gda,429)" #5, 
e@- “© — -90665185 
a 
These appear to have been derived from Captain Clarke’s de- 
termination of the elements of the figure of the earth which are 
as follows :— 
feet. metres. 
Major semi-axis of equator (longitude 15° 34’ east) =a = 20,926,350 =6378294:0 
Minor _,, A (oc: 105° 34’ ,, )=b=20,919,972=6376350°4 
Polar semi-axis =c= 20,853,429 =6356068'1 
It would seem that the equatorial diameter in longitude 152° 
east had been calculated and adopted with the above polar dia- 
meter as defining the spheroid of revolution on which to calculate 
the work. The adoption of spheroidal elements seems advisable 
for, notwithstanding that his determination, referred to above, 
indicates the earth to be of an ellipsoidal figure, Col. Clarke in 
1880, writes: “It is necessary to guard against the impression 
that the figure of the equator is thus definitely fixed, for the 
available data are far too slender to warrant such a conclusion.” 
The assumption has then been made that the earth is a spheroid 
of revolution with the first given set of elements and the com- 
putations made therefrom. The values. given for a surface of 
revolution by Clarke’s 1866 determination have been very generally 
adopted as most nearly representing the data, and have for many 
years been used on the United States Coast and Geodetic Survey 
as well as elsewhere. As it may be of interest to compare the 
