270

THE NEW ZEALAND GAZETTE.

from the centre of disturbance, and where the older
tertiary rocks come up to the surface.

In the Taranaki district this would be to the north
of New Plymouth, and in localities where perhaps
there might be no surface indications excepting those
which everywhere mark dislocations of the strata.

From the above considerations it is probable that,
in the neighbourhood of Sugarloaf Point, where
these explorations are being made, the boring will
have to be carried to a very great depth before a
constant or abundant supply of oil can be looked for,
unless, as is extremely probable, when sinking through
a rock which appears to be in parts saturated with
oil, an open cavity or fissure be accidentally struck
in which a large quantity of oil has accumulated.

Such natural cavities are frequently struck when
boring in the sandstone in America, the result being
a sudden and forcible discharge of gas, oil, or water,
according to whether the upper, lower, or middle
part of the cavity be first tapped; but before long
this spontaneous overflow always ceases, and then the
ordinary method of pumping has to be resorted to.

If, however, the oil has been condensed in the
fissures that traverse the trachyte breccia at Taranaki,
from the form of vapour, and if it does not percolate
freely through the substance of the rock, as it does
between the layers of sandstone and shale in
America, I fear that the pumping will not be of
much avail.

The specimens of petroleum submitted have been
carefully analysed in the laboratory of this depart-
ment, by Mr. Skey, and from the result of his
examination it would appear that the nature and
value in relation to other petroleum oils, of the
samples as yet obtained, has been somewhat over-
estimated, and that they must only be looked upon
as a good indication that really valuable oils may
exist in the neighbourhood.

All the various samples which have been submitted
have the same physical characters, having a dirty
green color by reflected light and being opaque,
except in thin films, when it has a deep red color by
transmitted light.

At 60° Fah. it is quite limpid, and though at
lower temperatures it has considerable consistency,
yet when reduced to 25° Fah. it does not become
solid.

It has a mawkish but not unpleasant odour, being
very different in this respect from most rock oil, and
is especially free from all traces of sulphuretted
hydrogen gas.

Minute flakes of a white substance, probably allied
to paraffine, float in the oil, and are gradually
deposited, when it is allowed to remain quiet at a
low temperature, nearly the whole of this solid
substance becoming dissolved when the oil is gently
heated.

The temperature at which the oil boils is 340°
Fah., and it does not appear to evaporate at ordinary
temperature for when exposed to the air it remains
unchanged, neither thickening nor acquiring a skin
on the surface.

Its temperature requires to be raised to 260° Fah.
before its vapour inflames; and even with a wick it
does not burn so freely as common animal oils.

The specific gravity is very high as compared with
other hydro-carbons, being no less than 962 (water
being 1000) or 14 degrees of Gesner's hydrometer
scale.

There does not appear to be any instance on record
of a rock oil having so high a specific gravity, the
usual range being from 814 to 930 for crude oil.

It may be explained that all the varieties of
petroleum are composed of carbon and hydrogen and
only differ in their quality occording to the proportion
which these two elements bear to one another, the
heavier, and inferior oils for illuminating purposes
having the larger proportion of carbon.

There is therefore no test of the quality of the oil
which is so reliable and so easy of application as that
of the specific gravity, and the above results are quite
sufficient to show that the samples of oil examined
have a much larger proportion of carbon in their
composition than the common petroleum from which
the kerosene of commerce is manufactured. This was
still further proved by the examination of the oil by
distillation as in the production of kerosene.

A measured quantity of the crude oil was distilled
with a very gentle heat which was gradually raised
until 80 per cent of the original quantity was obtain-
ed in the receiver, which is about the average pro-
portion of kerosene obtained from the American
petroleum.

The oil obtained which had a faint yellow color
and pleasant odour, was of specific gravity 930, which
is denser than the commercial proof that has been
fixed for heavy lubricating oils (927).

As the lighter oil would distil over first and at a
lower temperature, the experiment was repeated and
the process stopped when 25 per cent. of the original
quantity operated on had been obtained in the
condenser.

The distilled oil obtained on this occasion had a
specific gravity of 889 or slightly over the proof fixed
for light lubricating oils (881).

By further experiments it was found that the
lightest oil that could be drawn over had the specific
gravity of 874 and of this quality only a 1/2 oz. could
be obtained from 12 oz. of the crude oil after it had
been carefully purified by filtration.

The next 1 1/4 oz. obtained had a specific gravity of
893, and the next ounce 917, which would give to
the remainder of the 80 per cent. of distilled oil
obtained in the first experiment a specific gravity
of 941.

The first two samples were quite clear and color-
less, but the last had a pale yellow tinge.

The average specific gravity of the 2 1/2 oz. thus
obtained from the original quantity of 12 oz. was
900, or that of a lubricating oil of medium quality,
while the oil left in the retort had a consistency
of tar.

The ordinary density of the kerosene of commerce
should be 819 (although it is often made lighter, in
order to improve its color, which however renders it
liable to explode), and it has been found impossible
to obtain oil of this low density from Taranaki
petroleum.

The lightest distilled oil which was obtained burns
freely with a wick, but has a lurid flame, and though
not adapted for use in the ordinary kerosene lamp,
might possibly be used in a lamp suitable for para-
fine oil.

The residuem left in the retort when 80 per cent.
of oil was drawn over was a hard brittle pitch, which
can be obtained from the crude oil in the proportion
of 73 grs. to the fluid ounce.

This pitch when further examined gave 28 per
cent. of hydro-carbon evolved at a high temperature,
and 62 per cent. of a lustrous vesicular coke, which
contains 7.77 per cent. of ferruginous ash.

The general results of these experiments may be
tabulated as follows:---

One hundred parts of the crude oil, as obtained from
the wells, having a specific gravity 962, gives—

Distilled oil of specific gravity 874 ... 2
" ", ", 893 ... 10
" ", ", 917 ... 8
" ", ", 941 ... 60