(34)

diminished somewhat by notching and
the effective depth of the trusses is
about 10' 6", being somewhat less than one
thirteenth of the span. The greater the
span the greater the depth required for the
truss; the span in this case being consi-
derable, equal to the greatest of which I
have seen an example, the depth of the
truss should have been about the maximum
that is to say, about one-tenth of the span,
whereas it is less than the minimum of one
twelfth. Add to this defect in the depth
of the trusses the insufficiency in depth or
width of scantling, very partially compen-
sated for by the superior description of
wood the designer proposes to use, and it
will be evident that the bridge would not
bear even a comparatively moderate weight.
The designer has paid considerable attention
to the abutments and the approaches of the
bridge, to the details of construction, and
to the specification; it is a pity, therefore,
that he had not given a little more consi-
deration to the effective strength of the
main part of his design, which obliges me
to place it amongst those not eligible or
sufficient. I cannot give him credit for his
Estimate, which though in tolerable detail,
is quite insufficient: taking one item of
material alone, viz., Totara timber; the
price, exclusive of labour, is carried out at
£6 per thousand feet, 12s. per 100; now
considering that the price of pine is from
20s. to 22s. per 100 feet at New Plymouth,
as appears by several of the Estimates, and
that Totara is a superior hardwood, more
costly in preparation, it is not too much to
assume that its cost would be at least fifty
per cent above that of Pine. In point of
fact in one Estimate the rate of 35s. per
100 feet has been taken for Totara, which
I believe is not above the mark, if sufficient
to pay for its delivery on the spot; thus
the item for timber would be about three
times that taken in the Estimate for the de-
sign under consideration. As the item for
the abutments is not in detail I cannot ana-
lyze it, but it appears to me small consi-
dering there is a certain amount of cut
stone in it.

Having now considered each design, I
will remark that to endeavour to satisfy the
competing designers I have not confined
myself to giving a simple arbitrary deci-
sion, but have endeavoured to explain in
as popular terms as possible, and by refe-
rence to examples and actual experiments
which are more valuable than simple theory
unconnected with practice and experiment,
the reasons for my judgment. Doubtless
many parties will be dissatisfied, looking on
their designs with a partial eye, especially
as the only premium that I think ought to
be awarded will fall, if I mistake not, on a
Civil Officer under my orders, whose hand
writing in the specification I could hardly
avoid recognising. This recognition caused
me some momentary embarrassment, but it
made me feel the necessity of most cau-
tiously and impartially considering my
judgment, and having arrived at an opinion
it would have been a weakness and an in-
justice to have hesitated in recording that
opinion because it was in favor of a design
by a person I believed attached to my De-
partment. It may be also considered that
I have been over strict in not recommend-
ing the award of a second premium, but
when in my firm belief there was not a se-
cond design that was by any means eligible
or that ought to have been carried into ex-
ecution, either from defects of strength in
the bridge itself, insufficiency of abutments
or other causes, the recommendation of an
award would have been tantamount to a de-
ception of the Provincial Government who
might have carried the second design into
execution if apparently at first sight more
economical than the best design, (for ins-
tance Design No. 15, is very creditable in
many respects, and the Estimate low) to
their eventual grievous disappointment and
loss and my own discredit.

There is one more point to which I would
wish to direct attention, it is not adverted
to in the Prospectus but it is one upon
which the security of the bridge may most
material depend. It is understood that
trees are brought down the river by freshets
and so large as to require one span of up-
wards of 100 feet to admit of their passing
through if coming down with their length
across the stream; it is possible that these
trees may not be so denuded of branches
but that large limbs may be projecting
above the water sufficiently to catch the
roadway of the bridge, and corresponding
limbs be dragging on the ground at the
bottom of the river; thus checked in their
progress and to a certain degree acting as
a dam to the water running down with al-
most irresistible force, either the branches
of the tree or the bridge must yield. None
of the designs shew a greater height than 8
feet above the level of the water in the
highest freshets, and the best designer, No.
12, gives that clear height; whether this is
likely to be sufficient or not I cannot from
want of local knowledge decidedly state;
the question, therefore, should be maturely
considered on the spot, and, if requisite,
such increased height be given to the abut-
ments as will place the bridge clear of every
obstruction and danger. The cost of the
abutments and approaches, and of the ap-
pliances for raising the bridge would ne-
cessarily be somewhat increased, but this
should not be a consideration if the exist-