Volume I Part 27 (1/2)

MACDONALD'S RANGE.

Our first encampment was on the banks of a small river at a spot 2,640 feet from the sea. This river ran through a deep and narrow valley, descending with a nearly regular slope from a tableland of sandstone, in which it took its rise about seven miles inland. At this encampment the height of the bed of the river above the level of the sea was 188.76 feet, as found by the mean of several very accordant observations, which, at the same average slope, gives an elevation of about 377 feet for the height of a spot on its banks distant only one mile from the sea; and if we conceive the average increase of elevation to the sandstone tableland to be only 200 feet in every mile (and I believe it to have been more) we shall have 1400 feet for the elevation of the tableland which formed one of the highest parts of Macdonald's Range.

ELEVATION OF HILLS.

After pa.s.sing across this range we again descended rapidly into the low country, the face of which is much broken by conical hills composed of basalt. The heights of some of these hills above their base, which had a considerable elevation above the sea level, were in three instances as follows:

February 28.

The measured height of a hill above its base was 331 feet.

March 4.

Measured the alt.i.tude of a hill above its base and found it to be 222 feet.

March 8.

Measured the alt.i.tude of a hill above its base and found it to be 229.5 feet.

None of these hills had apparently near so great an elevation as the sandstone range of which they were under-features. At this period our barometer was unfortunately broken. We now proceeded up the banks of the Glenelg and arrived at many hills and conical peaks, apparently much higher than those I had measured; yet on afterwards pa.s.sing the river and attaining the summit of the opposite sandstone range, we looked down upon them as hills of far inferior elevation to those on which we stood. From this circ.u.mstance, and from the very perceptible change of temperature we experienced, I should think the alt.i.tude of the farthest point of Stephen's Range which we reached must have been 2,500 or 3,000 feet above the sea.

CHARACTER OF THE RIVERS.

The rivers in North-western Australia much resemble in character those of the south-eastern parts of the continent. They rise at no very great distance from the sea. Near their sources they are mountain torrents, but in the lowlands they become generally streams with slow currents, winding through fertile and extensive valleys or plains which are liable to sudden and terrific inundations, caused, I conceive, by the rain which falls in that part of the mountains where the rivers take their rise; for at one period, when we had our encampment on the bank of the small stream near the sea at Hanover Bay, I was myself distant about fourteen miles in the interior in the direction of its source, where we had heavy rain; and on my return I found that the party at the station had been surprised by a sudden rising of the water for which there was no apparent cause as there had been no rain where they were.

The Glenelg River, in like manner, is subject to sweeping inundations, rising sometimes to the height of fourteen to fifteen feet above its usual level, as was evinced by the weeds and other substances we saw in the trees on its banks.

To show that these are characteristics of the Fitzroy River I shall quote the authority of Captain Wickham from a letter addressed to me just before our meeting at Hanover Bay:

It (the Fitzroy) appears to be very similar to the rivers on the south-east side of New Holland, subject to dreadful inundations, caused by heavy floods in the interior, and in no way connected with the rainy season on the coast. Our visit to it being in February and March, immediately after the rainy season on the coast, without our seeing any indication of a recent flooding, although there were large trunks of trees and quant.i.ties of gra.s.s and weeds lying on the bank and suspended from the branches of trees from ten to twelve feet above the level of the river. The bed is entirely of sand.

INUNDATIONS.

It will be clearly seen how nearly this corresponds with what we observed about the same season on the banks of the Glenelg. I have therefore little doubt that the Fitzroy takes its origin from the same mountain chain, and that the inundations described by Captain Wickham originate in the causes which I have here a.s.signed.

To demonstrate more clearly the similarity of character of these rivers with those of New South Wales I shall quote two pa.s.sages from the British Colonies of Mr. Montgomery Martin, regarding the Hawkesbury and Hunter Rivers of that colony:

The Hawkesbury, which is a continuation of the Nepean River, after the junction of the latter with a considerable stream, called the Grose, issues from a remarkable cleft in the Blue Mountains in the vicinity of the beautiful town of Richmond, about forty miles from Sydney. Along the base of these mountains the Hawkesbury flows in a northerly direction, fed by numerous tributary mountain torrents, descending from narrow gorges, which, after heavy rains, cause the Hawkesbury to rise and overflow its banks as it approaches the sea. In one instance it rose near the town of Windsor ninety-seven feet above its ordinary level. Volume 4 page 257.

Again he says, page 258:

Hunter's River, about seventy miles to the northward of Port Jackson, disembogues into the sea at the harbour of Newcastle.

There are three branches to the Hunter, called the upper, the lower, and the middle: the two former are navigable for boats for about 120 miles, and the latter for about 200 miles; but the branches are all subject to sudden and terrific inundations owing to the rapid descent of torrents from the Blue Mountains.

MOUTH OF THE GLENELG.

In concluding my remarks on the rivers of the north-west I should state that Mr. Stokes, the surveyor of the Beagle, after a careful examination of the coast did not succeed in finding the mouth of the Glenelg; and he imagines that it has several openings, consisting of large mangrove creeks, which fall into Stokes Bay; whilst it is my impression that it will be found to run out somewhere between Camden Sound and Collier's Bay, and that by some accidental circ.u.mstance its mouth was missed. That it joins the sea in a considerable body I should infer from a shoal of porpoises having been seen high up the river, and from the rise and fall of tide, which was twenty feet at the direct distance of thirty miles from the coast.