On the Geology of the Gold-fields of Otago, New Zealand. By W. Lauder LINDSAY, M.D. & F.R.S. Edinburgh, F.L.S. & F.R.G.S. London, &c.

The author had made a personal geological survey of the Tuapeka and other goldfields of Otago between October 1861 and January 1862, some of the general results whereof were published, under the section on the "Geology of Otago," in a Lecture by him, printed in Dunedin in January 1862, entitled "The Place and Power of Natural History in Colonization, with special reference to Otago; being portions of a Lecture prepared for, and at the request of, the Young Men's Christian Association of Dunedin," and issued as a pamphlet by and under the auspices of the said Association.

He had also formed and brought home a considerable collection of the rocks and minerals of the Otago gold-fields, with relative field-memoranda, maps, and drawings. The general results of his observations and deductions may be tabulated as follows:

1. The gold and gold-bearing rocks of Otago do not differ essentially, quoad mineralogical or geological characters, from those of every other part of the world hitherto known to be auriferous.

2. The original matrix of the gold is quartz; and the latter occurs interbedded in, or associated with, metamorphic slates, especially of the gneiss, mica, tale, chlorite- and clay-slate families.

3. These slates vary greatly in mineralogical character; but they bear a closer resemblance to those of central and southern Scotland (Grampians, &c.) than to the more altered Silurian auriferous slates of Victoria (Australia).

4. The slates in question are probably of Silurian age; but this has yet to be proved, for they are themselves non-fossiliferous; and as yet the subjacent rocks are

unknown.

5. At various points there are evidences of considerable disturbance in the schistose strata by the intrusions and eruptions of trappean rocks, apparently referable to the Tertiary era.

6. The valleys among the schistose hill-ranges are generally occupied by alluvial drifts, apparently of Tertiary age, naturally divisible perhaps into a lower or older group, characterized by its abundant lignites, and a superficial or newer series, which is chiefly the seat of the operations of the gold-miner.

7. The lignitiferous or older drift consists chiefly of quartz gravels-in certain deposits cemented by means of peroxide of iron and other materials into a hard red conglomerate-associated with thinner strata of clays, sands, and gravels. This series of beds sometimes occurs at a height of from 500 to 1000 feet above the sealevel, on the flanks of trappean and other hills.

8. The upper or newer drift bottoms-the valleys and "flats," so common in the hilly parts of the country (where the hills are schistose)-consist essentially of (a) clays, blue, yellow, or red; (b) boulder-clays; and (c) gravels, so called, which are really the little-worn or abraded débris of the subjacent and circumjacent slates, and which are more correctly denominated by the miner's phrase," chopped slate." These beds are immediately superjacent (in the order in which they are above enumerated) on the generally upturned and very irregular edges of the slates; and the latter, according to their mineralogical character, give a dominant colourt o the former, the clays and gravels of the gneiss being bluish or greyish, of the chlorite-slates greenish, of the mica-slates, in proportion as they are less or more ferruginous, yellow or red.

9. Gold occurs chiefly in the gravel or "chopped slate" above described,―this constituting the "wash-dirt" of the miner. It is frequently found most abundantly in "pockets" (hollows or crevices) of the irregular upturned edges of the subjacent slates, whereon the gravel immediately reposes. It is disseminated through the clays in some localities; while in others it is sometimes collected in quantity in cavities, or "pockets," under the boulders of the boulder-clay beds.

10. The gold is partly granular or gunpowder-like, partly scaly, nuggety, or crystallized; and it exhibits every gradation, intermixture, and variety of each of these forms or kinds in different localities.

11. It is associated, in different localities, with iserine (titaniferous iron-sand);

iron-pyrites, common and arsenical (mispickel); cassiterite (tin-sand or oxide of tin); topaz (of the gouttes-d'eau character, blue or colourless); garnets, and other minerals.

Much of Otago remains yet to be explored, especially the mountainous western portion of the province; but, from the geological structure of those portions of the province he personally examined, the author draws or makes the following inferences, deductions, or predictions:

1. That the geological basis of the greater part of Otago consists of auriferous metamorphic slates. This refers especially to the great central and western mountain-ranges; for instance, those which encircle the large interior lakes (Hawea, Wanaka, and Wakatip).

2. That these great mountain-systems are probably the source of the tertiary drift so abundantly distributed over the lower parts of the province, which drift consists mainly of quartzose and schistose débris.

3. That this tertiary drift, in both its lignitiferous and more strictly auriferous series of beds, will be found much more extensively and largely distributed over the province than at present.

4. That gold is very extensively and largely distributed over the province; and that many gold-fields remain to be discovered, especially in the interior; though nothing short of actual mining, or "digging," can determine the localities of "payable gold-fields."

5. That the supply of gold is at present practically unlimited; and that the auriferous resources of Otago are only beginning to be developed, and will only be fully developed in the course of many years, by-a. The addition of quartz-mining, and others of the skilled branches of gold-mining, to the shallow or alluvial digging," to which the miner's operations are at present mainly confined. This implies a greater concentration of attention than at present on the auriferous quartzites, from which the drift or alluvial gold has originally been derived, the working whereof; should they exist to any extent, is much more likely to yield a permanently remunerative employment, and a permanent and valuable source of revenue, than the said "alluvial digging." b. The systematic application of improved chemical and mechanical, or chemico-mechanical, processes to gold-mining, and the expenditure thereon, or application thereto, of suitable capital. c. The establishment of goldmining as one of the permanent industrial resources of the province. d. The systematic prospecting, by exploring and experimental parties suitably equipped, partly geological and surveying, partly mining and "digging." e. The liberal and enlightened encouragement of mining and of the miners by the construction of rail- and tramways, the opening-up of roads, the building of bridges, the establishment of townships, the sale of waste lands at suitable prices, the adequate supply of fuel by the working of lignite-beds or otherwise, the institution of proper mining laws and mining boards, and other measures pertaining strictly to the legislative function of the State.

The following Tables illustrate the comparative prolificness of the Otago goldfields, from their discovery in June 1861 to the end of March 1862:

I. Showing the amount of gold brought to Dunedin by each Government escort from the chief gold-fields of Otago (compiled from the Receiving Officer's returns).

II. Showing the quantity and value of, and duty on, gold exported from Otago between 3rd August, 1861, and 31st March, 1862.

III. Showing the quantity and value of all the gold exported from the whole of New Zealand up to 31st March, 1862.

Tables I. and II. are compiled from statistics given in the 'Otago Daily Times' of April 6, 1862, and Table III. from those given in the 'Otago Colonist' of July 15, 1862.

On the Geology of the Gold-fields of Auckland, New Zealand. By W. LAUDER LINDSAY, M.D. & F.R.S. Edinburgh, F.L.S. & F.R.G.S. London, §c. The author had personally made a geological examination of the Coromandel gold-field, in the province of Auckland, in February 1862, having previously spent several months on a similar survey of the Otago gold-fields. He described Coromandel as a different type of gold-field from Tuapeka (Otago), and, as such, of interest as illustrative of the general geology of the New Zealand gold-fields. The main results of his observations and deductions may be concisely stated thus :-1. The geology of the northern gold-fields of New Zealand, including those of Nelson as well as of Auckland, does not differ essentially from that of the southern or Otago gold-fields (as the geology of the latter is described in his paper "On the Geology of the Otago Gold-fields," save in so far as regards certain minor details. The parent slates, for instance, are in the north more frequently of a clay-slate or argillaceous character than in the south; the auriferous quartzites are frequently developed to an extent as yet unknown in Otago; the evidences of trappean disturbance are more numerous, and the metamorphism of the slates by the contiguity of the erupted or intruded traps better marked. Nor does the character of the gold differ materially, save in so far as, in certain localities, it is more generally associated with its quartz matrix.

2. The Coromandel Peninsula consists mainly of a mountain ridge, running nearly north and south; the mountains having a bold serrated outline, and varying in height from 1000 to 2000 feet. The valleys between the spurs given off laterally by this main or dividing range are of the character generally of ravines or gorges, occupied by mere mountain streams; the "flats" or alluvial tracts at their mouths, and on the coast, are inconsiderable.

3. This mountain-range consists apparently of slates of Silurian age, generally of argillaceous character, but greatly altered by contact with, or proximity to, numerous outbursts or intrusions of trappean and other rocks. The mountains are so densely wooded, and so difficult of access, that it is only here and there in the gorges of the streams that sections of these slates may be examined. In these sections the slates are frequently found to resemble Lydian stone or the slaty varieties of basalt (such as clinkstone); while they are disposed more or less vertically, their irregular upturned edges affording the most convenient and abundant "pockets" for the detention and storage of the alluvial gold washed from the higher grounds.

4. [Local geologists describe the fundamental rock of the Coromandel mountainsystem as granitic, and the granite as forming here and there the "aiguilles" of the dividing ridge. The author met with no granite in situ; nor did he discover granitic boulders or pebbles in the boulder-clays of the auriferous drift, or in the shingly beds of the mountain streams about Coromandel Harbour.]

5. The Coromandel slates are characterized by their prominent and numerous quartz "reefs," consisting of auriferous quartzites. Here and there, where the dense vegetation admits, these reefs are met with in situ, frequently as "dykes," standing prominently above the general level of the slates; sometimes forming the top of the dividing ridge itself. The proximity and abundance of such quartzites are sufficiently indicated by the immense numbers of huge quartz-boulders or blocks which bestrew the low ground and occupy the ravines and gorges, which blocks are characterized by comparative angularity. The quartz is frequently of the porous, light, spongy character so prevalent in the gold-fields of Australia, Nova Scotia, California, and other auriferous countries; and its colour is frequently buff, brown, ochrey, or vermilion, the result, apparently, of different degrees of ferruginous impregnation.

6. The auriferous drift is mostly of the character of the newer or upper Tertiary drifts of the Otago gold-fields, consisting essentially of-a. variously coloured clays; b. boulder-clays, also variously coloured; and c. gravels, of the chopped slate