Yan Yean Water Works. 189 
still water, This swamp was composed of vegetable matter 
to an unknown depth, and so boggy, that a fencing rail was 
forced into it by one man to a depth of five feet; the flow of 
water at this point was so trifling that it could not be mea- 
sured, and was probably all evaporated before reaching the 
junction with the eastern arm. From minute inquiries we 
learnt that this swamp extended two and half miles further 
up, making in all four and half miles of swamp, averaging 100 
yards wide, thus exposing 787,000 square yards to surface 
evaporation. We did not follow this arm up to its source, 
but we feel satisfied that it affords little, if any, supply to the 
Plenty during the summer months, and on this occasion none. 
We then proceeded to examine the eastern arm, which 
also flows, with the exception of a slight divergence, through 
a swamp, for two and a half miles above its junction with the 
western arm. This swamp is two anda half miles long, and 
averages 700 yards wide, having, therefore, a superficial 
extent of 3,000,000 square yards; it is charged with water 
from the eastern arm, and is in some places less boggy than 
the western arm, and the flow of water through it has a more 
defined channel and consequently has a less proportionate 
evaporation. We measured this discharge about two miles 
up, and found it to be 712 cubic feet per minute, the surface 
velocity being 10°18 inches per second, and sectional area 14 
square feet, the mean velocity being obtained, same as in 
former case; it is thus 1? times the discharge of the Plenty, 
where previously measured at aqueduct below the swamp; 
thus showing, that at that time 43 per cent of the discharge 
was lost by evaporation in the swamp. 
Our next subject of inquiry was relative to the source 
from which the River Plenty derived its supply in the summer 
months, as it was perfectly evident that there was no surface 
drainage into it from its basin, excepting after heavy rains, 
the surface of the ground being quite dry, and the eastern 
arm the while discharging a strong current of water; to this 
end we determined to follow up the eastern arm to its source. 
Proceeding accordingly, we crossed Jack’s Creek, which is a 
fine tributary to the eastern arm, and through which a consi- 
derable volume of pure water was flowing; and pursuing the 
eastern or main arm, we crossed the Sugar Loaf Creek, 
which is another small tributary of good water being now at 
the foot of the Ranges, we again crossed the eastern arm at 
the Ford, and commenced ascending up a deep gully or gorge 
down which it flows. This gully is clothed with verdant and 
dense vegetation, consisting of tree-ferns, &c., increasing in 
