62 
THE TASMANIAN NATURALIST. 
To seaward the water is also consistently shallow and the rise and 
fall of ten or twelve feet of tide exposes wide mudflats and permit of 
such islands as Robbins and Perkins being easily reached on horseback 
at low water. Inland the low country varies in width from two to ten 
or twelve miles, being met on the south by the low hills usually basaltic 
that extend back inland, reaching a maximum height of about 800 feet. 
The small streams issuing from these hills, or from low basins 
among them, flow sluggishly through flat valleys with occasional swamps, 
usually low areas of land having ample fall for artificial drainage, and 
almost dry in summer, but generally covered with an inch or two of 
water in winter, owing to the heavy rainfall of about 50 inches, combined 
with the dense vegetation, and retentive nature of soil. These swamps 
have apparently been formed by the overflow of the rivers, the decay of 
the dense vegetation, or by the material deposited by the numerous 
springs that exist in many of them. One spring noted about a quarter 
of a mile from where the bones were discovered in the Mowbray swamp 
had raised a mound about half an acre in extent and thirty feet in height. 
Stretching back from Smithton, almost due southerly, is a long 
valley, bounded on each side by hills several hundred feet in height. 
The Duck River, and its southern branch the Rogers, runs through 12 
or 15 miles of the northern portion of the valley which ranges from a 
mile to several miles in width, but the valley extends on beyond where 
these streams enter it from the east, and after travelling three miles 
further over low and occasionally swampy flats some more streams are 
met with running down southerly to the Arthur River, a fine stream 
from two to three chains in width, running parallel with the north coast 
and entering the sea nearly 30 miles south of Cape Grim. As this 
* valley' extends from Bass Strait right through to the Arthur, there would 
seem to be good grounds for supposing that in some past age the latter 
river found its way into Bass Strait by way of the 4 valley ’ and thus 
formed the Mowbray swamp and other swamps along the route. Mr. 
E. W. Stephens, engineer in charge of the Balfour-Smithton railway 
survey, which runs through portion of this valley, has ascertained that the 
height of the Rogers, where the line crosses is 116 feet above sea level, 
and the Arthur crossing ranges from 90 summer level to just the same 
height as the Rogers at flood time, whilst the highest point of the inter¬ 
vening five miles of railway line only rises 60 feet above the Rogers, and 
yet he believes that a much lower line could be located, and considers 
that this theory in connection with the valley is probably correct. 
Another fact that strongly supports this view is, that the Arthur 
'River is the only stream in Tasmania in which the common black-fish 
is indigenous, and does not flow into Bass Strait. 
The best known swamp in this district is in the parish of Mow¬ 
bray, from which it takes its name, and comprises about seven thousand 
.acres of selected land on the west side of the Duck River, near its junction 
