May, 1938 
The Queensland Naturalist 
S7 
the custom to collect the gravel above river level by 
wheeling it in barrows across planks from island to barge 
When this method was no longer possible, owing to the 
complete removal of the islands, recourse was had to the 
use of grab and clam type dredges which filled accom- 
panying barges. (It is noteworthy that one of these 
craft, still called the “Gayundah,” once constituted 
almost the entire Queensland naval fleet.) 
More recently the practice has been introduced of 
combining the dredge and the barge into one quick- 
acting unit. These, on account of their draught, are 
unable to operate above the Seventeen-Mile Rocks. One 
result of this has been further to intensify the operations 
between that point and the city. 
Let us now consider as far as we may the distribu- 
tion of the gravels of the Brisbane River. I suppose a 
strict field naturalist, who wished to obtain information 
on this point, would don a diver’s helmet and personally 
explore the bottom of the river, but I must confess that 
my enthusiasm for the cause was not quite as fervid as 
that. Instead I did the next best thing, and consulted 
Mr. D. Fison, the Engineer for Harbours and Rivers, 
whose knowledge of the bottom of the Brisbane River 
from Mt. Crosby to Moreton Bay must be unique. 
As one might have anticipated, there is, on the 
whole, a decrease in the size of the pebbles constituting 
the gravels as one proceeds downstream. Thus at the 
Upper Shoal, below Ugly Gully, the boulders average 
about eight inches in diameter. Heavy gravels are com- 
monly found between this point and Seventeen-Mile 
Rocks. From there to Six-Mile Rocks are the somewhat 
lighter gravels which are so valuable commercially. As 
we approach the city, the size of the pebbles becomes 
smaller, until in the neighbourhood of Victoria Bridge, 
the so-called “pea-gravel” is met with. This can be 
traced as far as the New Farm reach, which may be re- 
garded as the lowest point of the stream in which pebbles 
are deposited. From there to the mouth of the river the 
bottom deposits are sands of varying coarseness and 
mud. 
While this outline gives a rough idea of the general 
decrease in the average size of the pebbles encountered 
as one proceeds downstream, I do not wish you to think 
that the change is uniform and regular, far from it. 
There is an apparently haphazard distribution of coarser 
and finer material in every reach of the stream, and 
indeed in nearly every individual bank, as is shown 
