traced by describing a semi-circumference on the height AB as a diameter.

14. What is a Cavetto, and how is it traced?

A cavetto is an ovolo, of which the centre C is in a perpendicular from the extreme projection of the moulding. It is traced by describing the quarter of a circumference from C as a centre. The second figure presents a cavetto reversed.

15. What is a Scotia, and how is it traced?

It is a hollow moulding, formed by several cavettos with different centres. The second figure represents a reversed scotia. The circular parts are described with the centres A and B.

16. What is a Cyma-recta, and how is it traced?

The cyma-recta is composed of an ovolo and a cavetto. To describe it, draw the line AB, and then divide the projection of the moulding into two equal parts by the perpendicular CD, and produce the line B: the point D will be the centre of the ovolo, and the point C of the cavetto, which together form the cyma-recta.

The flattened cyma-recta is a similar moulding. To trace it, it is necessary, after having divided the line AB into two equal parts, to construct an equilateral triangle on each of the parts. The points C and D will then be the centres of the arcs which form the moulding.

17. What is the Ogee, and how is it traced?

The ogee is a moulding composed of the same parts as the talon, but differently placed. Having joined the points A and B, we draw through the middle point of this line the line CD, parallel to the fillets A and B, and the points C and D, in which it meets the perpendiculars, are the centres of the arcs which form the moulding. If the ogee is flattened, the centres are the vertices A and B of the equilateral triangles, each constructed on the half of DC.

18. How do you trace this moulding, when its projection exceeds its height?

Having joined the points A and B, divide it into two equal parts AC, BC, and then draw IP perpendicular to CA at the middle point. Next, draw LN perpendicular to B at the middle point, but in a contrary direction. Then draw BN perpendicular to the fillet; after which draw NC, and produce it to P: then P and N will be the centres of the arcs. To give grace to this moulding, the part BC is sometimes made shorter than the part CA: in every other respect the construction is the same.

19. How are these mouldings to be used in combination ? They are not to be used at hazard, each having a particular situation to which it is adapted, and where it must always be placed. Thus, the ovolo and talon, from their peculiar form, seem designed to support other important mouldings; the cyma and cavetto, being of weaker form, should only be used for the cover or shelter of the other parts. The torus and astragal, bearing a resemblance to a rope, appear calculated to bind and fortify the parts to which they are applied; while the use of the fillet and scotia is to separate one moulding from another, and to give a variety to the general appearance.

The ovolo and cyma are mostly placed in situations above the level of the eye: when placed below it, they should only be applied to crowning members. The place of the scotia is universally below the level of the eye. When the fillet is very wide, and used under the cyma of a cornice, it is called a corona; if under a corona, it is called a band.

The curved contours of mouldings are portions either of circles or ellipses: the Greeks always preferred the latter.

SECTION II.

OF THE ORDERS OF ARCHITECTURE, AND THEIR PRINCIPAL PARTS.

1. How many orders of architecture are there?

Five: the Tuscan, the Doric, the Ionic, the Corinthian, and the Composite.

2. How many parts do we distinguish in each of the five orders?

Three the pedestal, the column, and the entablature.

3. Of how many parts is the pedestal composed? Three the plinth, the die, and the cornice.

4. Of how many parts is the column composed? Three: the base, the shaft, and the capital.

5. Of how many parts is the entablature composed? Three: the architrave, the frieze, and the cornice.

6. Are these three principal parts always found in each of the orders?

Not always; for, in giving the name of an order to an edifice, regard is not always had to the columns, but sometimes to the proportions observed in its construction. Sometimes, even, there are no columns; and often the pedestal is replaced by the plinth only.

7. How are the five orders distinguished?

The Tuscan is distinguished by the simplicity of its members, having no ornament; the Doric by the triglyphs which ornament its frieze; the Ionic by the volutes of its capital; the Corinthian by the leaves which ornament its capital;