I shall only express my regret that we were unable to make the centre or to gain the Tropic.

As regards the objects for which the expedition was fitted out, I hope it will be granted that they were accomplished, and that little doubt can now be entertained as to the non-existence of the mountain chains, the supposed existence of which I was sent to ascertain.

It would, however, have gratified me exceedingly to have crossed into the Tropic, to have decided my own hypothesis as to the fine country I ventured to predict would be found to exist beyond it.
My reasons for supposing which I thought I had explained in my first letter to the Secretary of State, but as it would appear from an observation in Sir John Barrow's memorandum, that I had not done so, I deem it right briefly to record them here.
I had observed on my first expedition to the Darling, in 1828, when in about lat.

29 degrees 30 minutes S.that the migration of the different kinds of birds which visit the country east of the Darling during the summer, was invariably to the W.N.W.Cockatoos and parrots that whilst staying in the colony were known to frequent elevated land, and to select the richest and best watered valleys for their temporary location, passed in flights of countless number to the above-mentioned point.

I had also observed, during my residence in South Australia, that several of the same kind of birds annually visited it, and that they came directly from the north.