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Introduction.

It is necessary that I should preface my report with a few remarks that will help the reader to judge how much reliance can be placed on the accuracy of the map accompanying it, and on the conclusions that I have arrived at.

In the months of January and February, 1872, I examined, under instructions from Dr. Hector, Director of the Geological. Survey of New Zealand, the Southland district. In October, 1873, I was appointed Provincial Geologist in Otago, and during the ensuing summer, I rode over the north-western part of the Province, from the Waitaki to the Clutha, and in March, 1874, I visited the north part of Stewart Island and several of the sounds on the west coast in the Government steamer "Luna." In the summer of 1874-5 I examined, principally on horseBack, the remaining part of the Province from the Clutha to the Waiau, thus completing my survey.

The map, on a scale of eight miles to an inch, provided me by the Provincial Survey. Department, was well adapted for making a reconnaissance survey, as it was very accurate and on a sufficiently large scale for my purpose. But before any detailed geological survey can be made of the Province, it will be necessary to prepare a topographical map, on a scale of not less than one inch to a mile, showing all the physical features of the ground; for it is simply [unclear: a] waste of time and money attempting to put geological details on to a map that does not shew the true position and shape of every hill.

It cannot be supposed that in such a rapid survey as I have made of the [unclear: Province], I could, single-handed, have filled in quite accurately all the boundaries of the different formations, but I feel tolerably confident in the general accuracy of the work, and hope that it will be found a safe foundation for future detailed surveys by the geological survey of New Zealand.

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The map accompanying this report has been reduced to one third of that furnished me by the survey office, as a larger one would be unnecessary and inconvenient for use when bound up with the report. I hold myself responsible for the whole of it except the valley of the Hollyford, and the northern boundary between the granite and the gneiss in the upper parts of Preservation and Chalky Inlets. These places I have not visited, but have filled in my map from the remarks on the rocks made by Dr. Hector in his report on his geological expedition to the west coast of Otago in 1863.

The sections are of course sketch sections, and only give roughly the relative altitude of the mountains. They are merely intended to be explanatory of the text, and make no pretence of having been drawn to scale.

In the arrangement of the report I have tried to bring out clearly the general geology of the Province, and in order to do this I have described the formations in stratigraphical order, and not by districts. This plan has the disadvantage of not enabling local geologists to find out the structure of their district so easily as if all that is known about it were brought together, but I hope that the copious index to localities will to some extent lessen this objection. On the other hand it has the advantage of obviating the necessity of constant repetitions, which are necessary when describing the same formation over again in each district.

In the section devoted to previous observers I have included all the various classifications that have been proposed for the rocks of New Zealand, for they have an intimate bearing on the geology of Otago, and a knowledge of them will give the reader a better idea of the differences of opinion that still have to be reconciled than he would have had if my remarks had been exclusively confined to this Province.

I have quoted rather largely from Dr. Hector’s reports on the geology of the Manuherikia Plains, and his narrative of geological exploration of the West Coast, for as they are printed only in the Provincial Government Gazette, they will not be accessible to most of my readers, while as he is the only other page 3geologist who has travelled over Otago, it is necessary that I should state his views as clearly as possible.

Many will no doubt think, if they do not say, that in the section on Physiography it would have been wiser for me to have kept Back some of the ideas there put forth until I was in possession of many more facts to test them by, and I am quite willing to allow that it would have been so. But I have thought that the publication of these views, however crude they may be, would tend to stimulate enquiry throughout the Province, and would enable many observers, who have not the technical knowledge necessary to work out points in structural geology, to take part in the discussion of questions which are extremely interesting and important, and by no means easy of solution.

During the last eighteen months a considerable number of Otago fossils have been presented to the Museum, and among them are several undescribed species. I have, however, thought it better not to describe these species at present, for Dr. Hector has taken to England with him large collections of fossils from all parts of New Zealand, to be described there, and it is better for us to wait until this is done.

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