HYDRO-ELECTRIC INSTALLATIONS. CXIX, 
Admitting that the conditions existing at that remote 
period, with the imperfect knowledge available to those 
then in authority warranted, the open conduit and loss of 
head which has been adopted, it by no means follows that 
the whole matter is not worth reconsideration in view of 
the facts set forth by Mr. Kilburn Scott and later experi- 
ence. The construction of the Cataract dam to its full 
height—notwithstanding the influence which was exercised 
to keep it down—seems now to be fully justified, and as it 
is probably the most allround successful engineering work 
yet constructed by the Government of the State, it opens 
up in connection with the paper before the Society the 
following queries :— 
1. What would be the length, diameter, and cost of the 
smallest main necessary to deliver the given supply direct 
to Potts’ Hill while utilising the whole head for friction ? 
2. What would be the extra cost of larger and stronger 
main, to give say, a 250 or 500 feet head at Potts’ Hill with 
average delivery ? 
3. Givena 900 feet head at Potts’ Hill, what horse power 
would be available from the supply at average delivery ? 
4, What would the power cost per horse power year in 
the form of electrical energy with the most modern appli- 
ances of hydraulic motors and electric generators ? 
There are many other questions which suggest themselves 
in this connection which might well occupy the attention 
of our student members; for instance, there is the supply 
of the higher levels of Sydney and the comparison of direct 
supply from such pressure main to local reservoirs above 
Crown Street. For instance, given a 500 feet head at 
Potts’ Hill, would it be more economical to supply direct 
to a service reservoir at 250 feet with friction, and thus 
lose one-half of the available head, or to utilise the head 
of the whole quantity for power, and by turbine pumps, or 
motor pumps re-raise the high level supply ? 
