is much softer than the petunse, when dug out of the quarry; yet this is the ingredient which, by its mixture with the other, gives strength and firmness to the work. The mountains whence the kaolin is dug, are covered on the outside surface with a reddish earth. The mines are deep; and the matter is found in glebes or clods. They prepare both these stones in a similar manner.

CHARLES. Pottery in general is made of clays or argillaceous earths, because they are capable of being kneaded, and easily receive any form, and acquire solidity and hardness by exposure to the fire; but I observe that porcelain is formed of the hardest rocks, reduced to an artificial clay or paste, by grinding them fine, and softening them with liquids.

SOPHIA. The oils that are added, soften them, I suppose, in a still greater degree, and render their texture smooth and uniform. The first oil, or varnish, is a whitish liquid substance, drawn from the hard stone of which the petunses are formed. They choose the whitest squares, and those that have the most streaks of green in them, for making the

oil. They prepare the petunses for this purpose, in the same manner as for making squares. When reduced to this state, it is mixed with a mineral stone, called shekau, or kehao, resembling alum, which they first heat red hot, and then reduce into an impalpable powder: this gives the oil a consistence; but it should not be made too thick, as it is still to be kept in a liquid state. The fourth ingredient is the oil of lime, which requires a more tedious and difficult process. After dissolving large pieces of quick lime, and reducing them to a powder by sprinkling water on them, they put a layer of fern on this powder, and on the fern another of the slaked lime; and so on alternately, till they have heaped a moderate pile, to which they set fire. When the whole is consumed, they compose another pile of layers of the ashes, and new layers of dry fern, which they burn as before. This operation is repeated five or six times, the oil being reckoned better the oftener the ashes are burned. A quantity of these ashes of fern and lime is thrown into

an urn filled with water, and to one hundred pounds of ashes is added one pound of shekau, which dissolves in it. The rest of the process is the same as in preparing the earth of the petunses. The sediment found at the bottom of the second urn, kept in a liquid state, is called the oil of lime, from which the porcelain derives its principal lustre.

CECILIA. I am not surprised at the superiority of porcelain to common earthen-ware, now I am acquainted with the various processes used to prepare materials for the elegant purposes for which they are designed.

MRS. HARCOURT. As you have described the materials of this manufacture, and the manner of preparing them for their several uses, we must be contented to reserve the account of the various methods of forming them into vessels, figures, &c. till a future opportunity, as a particular engagement obliges me to leave you rather earlier than usual this evening.

67

CONVERSATION XIX.

TELESCOPE AND MICROSCOPE.

AUGUSTA. My father has promised to take me to-morrow to see a gentleman's museum, which is filled with rarities and valuable curiosities. Among other things, he tells me that there are several philosophical instruments, and that I am to see a variety of experiments. I should anticipate a great deal of pleasure in this visit, were I not entirely ignorant of the subjects with which I am to be entertained. So many things arise in my mind, which I wish to enquire about, lest I should expose my ignorance before strangers, that I find it difficult to select the questions most necessary to ask.

MRS. HARCOURT. A consciousness of our defects, is the first step towards improvement. A young lady of your age, is not expected to be deeply skilled in philosophy; much less to display her knowledge, should she possess a small share: but a general acquaintance with

the uses of the most common philosophical instruments, is not only ornamental, but also a very useful accomplishment, and should form part of every liberal education.

AUGUSTA. My father mentioned several particulars that are to be shown me: telescopes, microscopes, and an orrery especially; but I am quite unacquainted with the purposes to which any of them are applied.

MR. HARCOURT. In order to prepare your mind for your intended visit, we will defer our conclusion of the porcelain manufacture till our next meeting, and endeavour to explain the uses to which some of the most common philosophical instruments are applied. To enter into a description of their construction, or an explanation of their parts, would be ununinteresting and tedious, unless we had the machines before us. We will begin with the telescope, as presenting the most conspicuous, important, and noble objects in nature. It is an optical instrument, consisting of several glasses or lenses fitted into a tube, through which remote objects are viewed as if near. Before the invention of the telescope, the won