1918.] The N.Z. Journal of Science and Technology. 217 
Human bones, as also those of dogs, fish, and birds, were found in the 
shell-heaps. In one case nearly all the larger bones of (apparently) a young 
man or woman were found at one spot, possibly the relics of a cannibal feast 
of pre-European times. 
Between Te Paripari and Hongoeka (in Porirua Harbour) no shell-heaps 
are seen. The refuse from the settlements at Pukerua and Wairaka would 
have been cast over the cliff-head, and so, in later days, become covered 
with debris. 
A number of flakes of obsidian were found at Paekakariki, evidence of 
a system of barter among native tribes in former times, for this useful 
material, flakes of which were used as knives, must have been conveyed 
hither from northern regions. Flakes of a form of chert of a pinkish colour 
were also found, probably the refuse of some implement-maker. This kind 
of stone is called manutea by Taranaki natives, who fashioned adzes from it. 
NEUTRAL POINT ON A DELTA-CONNECTED SET OF 
THREE-PHASE TRANSFORMERS. 
By E. E. Stark, B.Sc., F.A.I.E.E. 
At Dunedin, New Zealand, in 1906 the writer advocated the use of a star 
system of distribution for the Waipori electric system. It had been proposed 
by the city’s contracting firm to install a delta system of distribution. The 
final lay-out of the transforming-system installed is as follows : A trans¬ 
mission scheme consisting of delta star-connected transformers at the power¬ 
house, with a neutral on the 35,000-volt high-tension side grounded. At 
the receiving-station the transformers were connected on the high-tension 
side in star with the neutral grounded, and the 3,000-volt low-tension side 
in delta, thus giving no available neutral for a local distribution at 3,000 volts. 
For simplicity of regulation on the independent phases of a three-phase 
system undoubtedly the star system lends itself better than the delta system, 
one other advantage of the star system being in its capacity to deliver a 
single-phase supply over one wire, using the earth as a return. The usual 
advantage of a delta-connected set of transformers, in that two transformers 
can be operated as an open delta, still exists with a star system if the neutral 
has a return either by separate wire or by earth ; and besides this there is 
the usual advantage of using lower-voltage transformers than could be done 
in the delta system of connection. 
With these advantages in view the writer set to work to devise a means 
to meet the change, as the step-down transformers had already been ordered. 
It was found impossible to alter the secondary winding of these transformers, 
and, further, it was considered that the mixed connection of star to delta 
with three transformers has a limited tendency to equalize the out-of¬ 
balance of the loads on the various phases. This out-of-balance condition 
is almost inevitable in a system supplying large single-phase loads. 
Various schemes of static transformers and choke-coils were proposed 
for obtaining the artificial neutral from the delta system, but abandoned, 
as these systems did not transfer the energy from a lightly-loaded higher- 
voltage phase to a heavily-loaded low-voltage phase. 
