of Taranaki, Mr. Trinhook of Hawke’s Bay, Mr. H. T. Kemp of the Bay of Islands, to the Missionaries, and to almost innumerable friends in Auckland.

Preliminary Remarks.

I cannot suppose that all my audience are acquainted with the first principles of Geology. I shall therefore be under the necessity, in order to make my report intelligible, of prefacing a few remarks upon the chief divisions of the Geological formations.

The various rocks, soils, and minerals, which occur upon the surface of the earth, or at various depths "beneath it"—in one word, the materials of the "earth’s crust"—are classified, in the first place, with reference to their different origin, or, in other words, with reference to the different circumstances and causes by which they have been produced. They are divided into four great classes—Plutonic, Metamorphic, Aqueous, and Volcanic rocks. Another mode of classification is with reference to their age—that is, to the comparative periods of their formation. Those divisions will be easily understood.

The Plutonic rocks comprehend all the granites, syenites, porphyries, diorites—rocks which agree in being highly crystalline, unstratified, and destitute of organic remains—which are considered as of igneous origin, formed in the earliest periods of the earth, in great depths, and cooled and crystallized slowly under great pressure.

The Metamorphic rocks are the crystalline strata, or schists, called gneiss, mica-schist or mica-slate, chlorite-schist, hornblende-schist—also destitute of organic remains. According to the most probable theory, these strata were originally deposited from water in the usual form of sediment, but were subsequently altered by subterranean heat, so as to assume a new texture.

The two first classes of rocks are usually found in such a position that they form the foundation on which the aqueous rocks were afterwards superimposed. For instance, they compose the central line of a range of mountains, on both sides of which sedimentary rocks are deposited. Thus, in reference to their age, they are considered as the oldest, and are therefore called also Primitive.

There are exceptions to this rule in reference to the age of certain plutonic rocks of eruptive character. But I am now stating only general principles, and therefore avoid all questions leading to scientific discussions.

The next in order are the aqueous rocks—the production of watery action. They are also called sedimentary rocks, from the fact that they are the hardened sediments accumulated at the bottom of the sea or of fresh-water lakes. They are stratified, or divided into distinct layers or strata: as, for example, clay-slate, marl, sandstone, limestone, and are divided into three kinds, called arenaceous or siliceous, argillaceous or clayey, and calcareous or chalky—according to the respective predominance of Silica, Alumina, or Lime. Rocks of this class cover a larger part of the earth’s surface than any others, and are of the greatest interest on account of the organic remains which are found imbedded in the different strata.

There are two principal means of ascertaining the relative age of aqueous rocks—derived, the one from their position, the other from the fossil remains they contain.

With reference to position—the bed which lies uppermost, is of course the newest of all, and that which lies at the bottom, the most ancient.

With reference to the fossils it is not so easy to give an explanation in few words; but some idea may be formed from the well-ascertained fact, that certain animals have existed for a certain period, and then wholly disappeared and been succeeded by other animals of different species, which, in turn, have again given place to others.

So, as Sir Charles Lyell truly says, “a series of sedimentary formations is like volumes of history, in which each writer has recorded the annals of his own times, and then laid down the book with the last written page uppermost.” And the organic remains are, as Dr. Mantell beautifully expresses it, the “coins of Creation,” which give us the means of tracing the history of the development of the organic kingdoms.

Thus, by superposition and by their organic remains, the aqueous rocks are divided into groups forming, in reference to their age, what is termed an “ascending series,” or beginning with the oldest, in the following manner:—

1. Primary formations or periods.
2. Secondary " "
3. Tertiary " "
4. Quaternary " "

In reference to the word “quaternary” I may explain that, although it is not an English word, I take the liberty to use it in the sense of “post tertiary,” as following the analogy of the other terms.

Each of those formations is again divided into numerous minor systems, on which I have no time to enter.

The fourth and last great division of rocks are the volcanic—as Trachyte, Basalt, Breccia, and Tuff—all produced by supramarine or submarine volcanic eruption. It is ascertained that the earliest true volcanic eruptions have occurred subsequently to the Secondary period, commencing in the Tertiary, and continuing to the present time; and it is a marked difference between the older and the more recent eruptions.

I have prepared a diagram which will serve to impress these first principles upon your memory, and so enable you to follow me in the account I have to give:—

DIAGRAM.

With these preliminary remarks, I now proceed to the main subject of my lecture.