VALUE OF AUSTRALIAN LONGITUDES. 
195 
is 0*51 seconds. The Australian astronomers, in their report — (6) 
page 31 — adopted the value (£„), which course, considering the 
circumstances surrounding the two determinations of this interval, 
was no doubt the best. 
(?/) Singapore to Port Darwin. — This interval was determined in 
1S83, the observers being Captain (now Major) L. Darwin, R.E., at 
Singapore, and myself at Port Darwin. Captain Darwin made his 
time observations with the transit instrument previously used by the 
British Expedition of the Transit of Venus in New Zealand in 1882, 
and I observed with an excellent portable transit instrument (3| inches 
object glass). The observations were recorded by chronograph. 
Galvanic signals were exchanged directly between the stations, sent 
by hand, and observed by reflecting galvanometer at each receiving 
observatory. Our personal equation was determined before the under- 
taking at Melbourne, and experiments were made at Melbourne and 
Sydney to test our mode of observing and transmitting signals. Three 
different methods were used in exchanging signals, in accordance with 
a plan proposed by Captain Darwin, which was strictly adhered to 
throughout. This plan is described in (6) page 26. The operations 
were repeated on the nights of February 13, 14, 15, 22, 23, 25, and 26. 
The two cable lengths Singapo re-Ban joewangie and Baujoewangie 
to Port Darwin were joined ; and the signals, though passing through a 
distance of over 2,000 miles, were satisfactory when the circuit was 
good. On some occasions they appeared unsteady ; but the greater 
attention theQ required in observing them seemed to compensate for 
their inferior quality, as the individual results show. 
(v) Difference of longitude between the flagstaff on Fort 
Canning (position of 1871) and Lieut. Norris’ station at Singapore in 
1882. This latter is the same as that occupied by Captain L. Darwin 
in 1883. This value is given in (15) page 68, and was determined by 
measurement by Lieut. Norris. The flagstaff was west of Lieut. 
Norris’ station. My station at Port Darwin was on the ground of 
the Eastern Extension Telegraph Company, 56 feet N. 40*22° E. 
of the veranda post at the north-east corner of the cable officer’s 
quarters. It was marked by a masonry pillar 4x2x2 feet, upon 
which the transit instrument stood. This point is now the origin of 
the Australian longitudes (6). 
( w ) Singapore- Baujoewangie. — Observers : Captain Darwin at 
Singapore, and Captain H. Ilelb of the general staff, Batavia, at 
Baujoewangie, Captain Ilelb made his time determinations by 
observing zenith distances with a portable universal instrument. 
Galvanic signals were exchanged on February 17, 18, 19, 21, and 
23, 1883. The personal equation between the observers was not 
determined — (G) page 29. 
(«0 Baujoewangie to Port Darwin . — This interval was determined 
by Captain Helb and myself. Signals were exchanged on four 
nights — viz., January 28, February 1, 22, and 23, 1883. Personal 
equation between the observers not known. 
These operations were arranged at the request of the Dutch 
Government in, order to verify the longitudes of Batavia. We were 
glad to have Captain Ilelb’s co-operation, as it was not certain 
whether the direct signals between Singapore and Australia would be 
