The paper upon which you intend to paint must be fixed in a straining frame, in order that you may be able to place it between you and the light, when you see occasion in the progress of your work. After tracing in your design, the colours must be laid ou in the usual method of stained drawings. When the tints are go in, you must place your picture against the window, or a pane of glass framed for the purpose, and begin to strengthen the shadows with Indian-ink, or with colours, according as the effect requires, laying the colours sometimes on both sides the paper, to give greater force and depth of colour. The last touches for giving final strength to shadows and forms, are to be done with ivory-black, or lamp-black, prepared with gum-water, as there is no pigment so opaque and capable of living strength and de

cision.

When the picture is finished, and every part has got its depth of colour and brilliancy, being perfectly dry, you touch very carefully on both sides, those parts which are to be the brightest, such as the moon and fire, and those parts requiring less brightness on one side, with a varnish made by dissolving one part of gum mastic and one of Canada balsam, in two parts of rectified spirits of turpentine; or mastic varnish alone will answer the purpose. You must be cautious with the varnish, as it is apt to spread. When the varnish is dry, you tint the flame with redlead and gamboge, slightly tinging the smoke next the flame: the moon must not be tinted with colour.

Ground glass is also a very good substance to paint upon for transparencies. If you touch any part with varnish, it will render that part transparent; and the rest may be painted in oil colours thinned with spirits of turpentine, or varnish. To paint upon linen or silk, it must first be done over with isinglass size, and then may be painted upon with distemper or oil colours.

In transparencies much depends upon the choice of the subject, and none is so admirably adapted to this species of effect as the gloomy gothic ruin, whose antique towers and pointed turrets finely contrast their dark battlements with the pale, yet brilliant moon. The effect of rays passing through the ruined windows, half choaked with ivy, or of a fire amongst the clustering pillars and broken monuments of the choir, round which are figures of banditti; or others whose haggard faces catch the reflecting light these afford a peculiarity of effect, not to be equalled in any other species of painting. Internal views of cathedrals also, where windows of stained glass are introduced, have a beautiful effect.

The great point to be attained is a happy coincidence between the subject and the effect The light should not be too near the moon, as its glare would tend to injure her pale silver light; those parts which are not interesting should be kept in an undis

tinguishable gloom, and where the principal light is, they should be marked with precision. Groups of figures should be well contrasted; those in shadow crossing those that are in light, by which means the opposition of light against shade is effected.

BOOKS ON DRAWING.

Kirby's Improvement of Brook Taylor's Perspective, 4to. The Jesuit's Perspective by Chambers, 4to. Ferguson's Perspective, 8vo. Malton's Perspective with the Appendix, fol. On the Projection of Shadows, in Nicholson's Principles, of Achitecture, 3 vols. 8vo.

PART IX.---GEOGRAPHY.

GEOGRAPHY is that science which teaches and explains the nature and properties of the earth, as to its figure, place, magnitude, motions, celestial appearance, &c. together with the various lines, real and imaginary, on its surface. The relation which Geography bears to Astronomy is well known. It is, therefore no wonder that the ancients, with all the genius and penetration we may be inclined to allow them, should not attain to the same degree of knowledge with the moderns, when we consider, that they were not assisted by the same helps. The moderns, in the discovery of America, have opened a passage to a New World, which was entirely unknown to the ancients; and those parts of the Old World which our forefathers thought uninhabitable, have been found to be inhabited; their torrid zone has been found to be temperate, it being refreshed by showers, constant breezes, and cold nights, by the direct setting of the sun, and the interposition of the whole body of the earth. Antipodes which have been the subject of much controversy, are now demonstrated to be matter of fact; and the globe itself has been compassed with less difficulty by Magellan, Drake, Anson, Cook, &c. than the Phoenicians and Greeks could have coasted the shores of the Mediterranean sea.

FIGURE OF THE EARTH.

The earth is a sphere or globe, whose surface is covered with land and water; and is therefore called the Terraqueous Globe. That the earth is spherical or globular will appear, not only from the circular shadow it has upon the Moon, when that body happens to be eclipsed by it; but also from the appearance of the sea, and the many observations made by persons standing upon

the shore, and viewing a ship departing from the port: they first lose sight of the bottom of the vessel, whilst they can still see the rigging and the flags at the tops of the masts; but as the ship recedes farther, they lose sight of those also, as if the whole were sunk into the deep. Likewise, if a ship sail towards the land, the mariners first descry the tops of steeples, trees, &c. pointing above the water; next they behold the buildings themselves; and, lastly, the shore; which can only be caused by the earth's rotundity.

The velocity of those parts of the earth which are situated near the equator, exceeds the velocity of those parts which are situated in higher latitudes. This being the case, the particles of the earth near the equator have a greater force to recede from the axis than the particles in other latitudes have. Again, as water is more susceptible of being agitated by the rotation of the earth than the land, it follows, that the waters would rise up towards the equator, and overflow all the land there, if the earth were a perfect sphere. To prevent which, it is necessary that the convexity of the earth, should be somewhat higher at the equator than at the poles. This would produce a difference in the lengths of the equatorial and polar diameters. From some observations which were made on pendulum clocks, fitted to beat seconds in the latitudes of London and Paris, it had been found, that their motion was slower as they approached toward the equator; and the pendulums were obliged to be shortened about a tenth part of an inch, in order to make the clocks agree with the times of the stars passing the meridian. This difference in the lengths of the pendulums appearing to the celebrated Huygens, and Newton, to be a greater quantity than could arise merely from the alterations by heat, they separately found that the earth must be flatted at the poles; and Sir Isaac Newton has shewn, in his Principles of Natural Philosophy, that this flatness is about 17.1 miles, and that the polar diameter is to the équatorial diameter as 229 to 230.

With regard to the constituent parts of the earth, "it seems probable," Says Sir Isaac Newton," that God in the beginning formed matter in solid, massy, hard, impenetrable, moveable particles, of such sizes and figures, and with such other properties, and in such proportion to space, as most conduced to the end for which he formed them; and that these primitive particles, being solid, are incomparably harder than any porous bodies, compounded of them, even so very hard as never to wear or break in pieces, no ordinary power being able to divide what God himself made one in the first creation. While these particles continue entire, they may compose bodies of one and the same nature and texture in all ages; but should they wear away,

or break in pieces, the nature of things, depending on them, would be changed. Water and earth, composed of old worn particles and fragments of particles, would not be of the same nature and texture now with water and earth composed of entire particles in the beginning. And therefore, that nature may be lasting, the changes of corporeal things are to be placed only in the various separations and new associations and motions of these permanent particles: compound bodies being apt to break, not in the midst of solid particles, but where those particles are laid together, and only touch in a few points." Hence we may conclude, that from these primary particles all other bodies are formed, whether they be metals, stones, salts, earths, vegetables, or animals.

Geographers have found it necessary to imagine certain circles to be drawn on the surface of the earth, for the better determination of the position of places thereon.

These are either greater or lesser circles; great circles divide the globe into two equal parts, the lesser circles divide it into two unequal parts.

There are six kinds of great circles; two of them, viz. the Equator, or Equinoctial, and the Ecliptic, are fixed; but the others, viz. the Meridians, the circles of Longitude, the Horizons, and the Vertical circles, are variable, according to the part of the globe they are appropriated to.

There are two points on the surface of the terraqueous globe, called the Poles of the Earth, which are diametrically opposite to each other; the one is called the North, and the other the South Pole.

The Equator is that great circle which is equally distant from both the above-mentioned poles, and is so called from its dividing the terraqueous globe into two equal parts, named from the poles which are situated in each, the northern and southern hemispheres. It is also called the Equinoctial, because when the sun enters it, the days and nights are of equal length in all parts of the globe. Seamen commonly call this circle the Line.

Meridians or Circles of Terrestrial Longitude, are supposed to be drawn perpendicular to the equator, and to pass through the poles: they are called Meridians, or Mid day Circles, because when the sun comes to the meridian of any place it is noon, or mid-day, at that place.

Hence every particular place on the surface of the terraqueous globe hath its proper meridian, and consequently a traveller who doth not directly approach to, or recede from one of the poles, is continually changing his meridian.

With respect to the two circles above described, every place upon the earth, is said to have its particular latitude and longitude

The latitude of any place upon earth is its distance from the equator, in a direct line towards one of the poles; and since the meridians proceed in such a direct line, therefore latitude is reckoned in degrees, and parts of degrees, on the meridians of the place.

The longitude of any place upon the earth is the east or west distance of the meridian of that place, from some fixed meridian, at which longitude is supposed to begin. Now, since all the meridians pass through the poles, they coincide with one another at those points, and their greatest distance from each other will be when they are farthest from those points of coincidence, viz. at the equator; therefore, longitude is reckoned in degrees, and parts of a degree, of the equator..

Geographers have differed very much in the meridian from whence they have assumed the beginning of longitude; the ancients, chose the meridian of the Canaries, which they called the Fortunate Islands: others have pitched upon the Azores, or the Western Islands; but the most usual way is now to reckon longitude from the capital of that country in which an author writes, and accordingly the longitude is reckoned in this work

from the meridian of London.

Parallels of latitude are small circles drawn parallel to the equator at any assigned distance therefrom; therefore every particular place on the surface of the terraqueous globe hath its proper parallel of latitude.

There are four of these parallels of latitude that are particularly remarkable, viz. the two tropics, and the two polar circles; but for the better explanation of those properties it will be necessary, first, to define the ecliptic.

The Ecliptic is that great circle in which the sun seems to perform its annual motion round the earth; this circle makes an angle with the equator of 23° 29'; it intersects it in two opposite points called the Equinoctial Points; and those two points in the ecliptic, which are farther from the equinoctial points, are called the Solstitial Points.

The tropic of Cancer is a parallel of latitude 23° 29′ distant from the equator in the northern hemisphere, passing through the northern solstitial point of the ecliptic, as before described: And,

The tropic of Capricorn is a parallel of latitude, as far distant in the southern hemisphere, passing through the southern point.

The arctic polar circle is a parallel of latitude 23° 29' distant from the north pole; and the antarctic polar circle in a parallel of latitude as far distant from the south pole.

The tropics and polar circles divide the globe into five parts,