230 PROCEEDINGS OF SECTION A. 
lengths along the parallels being, as with the other lines, checked 
by triangle chains, the angles of which were measured with 8-inch 
and 10-inch theodolites. 
After a considerable amount of this work was done, it was 
found that it was not proceeding expeditiously enough to meet 
the calls upon it, principally because of the inadequate funds set 
apart for the conduct of the scheme, and it was resolved to carry 
on a primary triangulation so as to reach the more distant parts 
of the colony, advantage being taken of a number of trigono- 
metrical stations having been marked for such a purpose a few 
years earlier by Captain Clarke, R.E., the then Surveyor-General. 
In 1860, therefore, a base nearly 5 miles long was laid down on 
the Werribree Plains, and measurement wasmade between January 
and May of that year, an extension of the base of triangulation 
to Green Hill, making the total length over 5} miles, being effected 
shortly afterwards. 
The actual measurement was made by the use of three iron rods, 
the lengths of which were ascertained by micrometer comparisons 
with the 10-foot ordnance standard lent by the New South Wales 
Government, a similar standard for use in Victoria being subse- 
quently obtained from the Ordnance Survey Department in 
England. The bars were fitted with steel ends, one flat and the 
other rounded to form a section of a sphere of 5 feet radius. 
They were used by being placed in series, with distances of about 
4 of an inch between the spherical end of the one and flat end of 
the adjacent one, the distance of these two apart being obtained 
by passing a wedge between them until contact with each other 
was made, the position of the wedge at the time being read by 
graduations made along its length. The wedge was of hard bell- 
metal, 7 inches long by 2 broad and the inclination of the faces 
was 30 minutes. The bars were kept level during the measure- 
ment, change of height being seldom needed, as the difference of 
height of the two ends of the base was only about 14 feet. A 
re-measurement of part of the southern end was made following 
the slopes of the ground, and on reduction the co-incidences were 
such as to justify the assumption that by the original measure- 
ment, the Werribree base was probably as accurate as any measured 
up to that time. The total difference between the two values for 
the southern part was 0-308 inches, or about 0°15 inches per mile. 
The terminals of the base were marked in a substantial manner, 
and immediately on its completion, triangulation was carried 
therefrom to the Western district by Mr. A. C. Allan, Messrs. 
Penniger, Black, Petty, and others being similarly employed in 
other districts. Considerable activity was shown for some time, 
the greater part of the colony being within a few years covered 
with a first class series of triangles, the last operation of the staff 
being the demarcation in 1872 of the straight line from the 
