TRIGONOMETRICAL SURVEY OF NEW SOUTH WALES. 229 
was obtained by the Talcott method of zenith pairs, the other 
latitude determinations being by measurement of circum-meridian 
altitudes, and by prime vertical transits. In addition to the 
astronomical observations at the stations connected with the 
triangulation, observations have been made to determine the 
latitude and longitude of a number of other points, distributed 
over the area of the colony, and shown on the map marked F. 
In connection with the survey of Brisbane a triangulation has 
been made from a base 1,924 feet long, laid down in the Botanical 
Gardens. The base was measured twice with one of the tapes 
inentioned as being used on the Jondaryan base, and once with 
the other of the same tapes, a fourth measurement being made 
with a new tape. The angles were measured with 10-inch and 
6-inch theodolites, and connection with the main triangulation 
shows differences of four seconds in azimuth, and about four-fifths 
of an inch per mile in length, representing a difference of about 
three-tenths of an inch in the length of the Brisbane base. 
The whole of the triangulation was in the executive charge of 
Mr. R. Hoggan, who was assisted by Mr. R. McDowall. 
VICTORIA. 
The trigonometrical survey of Victoria was preceded by a 
system of laying out on the ground, meridians and parallels of 
latitude, by which it was expected to rapidly meet the demand 
for land, which in 1857 the Survey Department found itself 
unable to cope with. The intention was to surround large areas 
by carefully fixed meridians and parallels, to subdivide these again 
into blocks of one-tenth of a degree in each direction, the further 
subdivision for alienation purposes being effected by contract. 
This work was begun in 1858 under the direction of Mr. R. L. J. 
Ellery, C.M.G., F.R.S., etce., the difference of longitude between 
Williamstown Observatory and the first meridian line being laid 
out on the ground by triangulation. 
The general course followed was to determine the direction of 
the true meridian by means of a transit instrument or an 18-inch 
altazimuth, placing marks in the direction of the true north and 
south at the greatest distances commanded by the observing 
station. These varied from 5 to 20 miles, but intermediate points 
were also marked where possible, the whole line being subse- 
quently run and, if on Crown lands, cleared and marked. For 
the chaining, the ordinary 66-foot chains were used, but distances 
were controlled by a subsidiary chain of triangles with sides of 
from 2 to 5 miles length, carried along the line from carefully 
measured bases. The intersections of parallels with the meridians 
were marked, and the parallels laid out both by offsets from 
chords and from tangents at right angles to the meridian lines, 
