Contour line

“ Soundings are supplemented by depth contours, lines connecting points of equal depth. These lines present a picture of the bottom. The types of lines used for various depths are shown in Section I of Chart No. 1. On some charts depth contours are shown in solid lines; the depth represented by each line is shown by numbers placed in breaks in the lines, as with land contours. Solid line depth contours are derived from intensively developed hydrographic surveys. A broken or indefinite contour is substituted for a solid depth contour whenever the reliability of the contour is questionable. ”

“ Lines drawn through the points of intersection will give the elevation of the cone. To find the inclination of the surface of the cone, upon a b, a portion of the normal D E, as a base, erect a perpendicular b c, equal in height to the distance of the sections apart, and join a c. The hypothenuse a c then represents that portion of the surface of the cone which is included between the two contour lines, and of which [38] the angle of inclination is b a c. The space between two contour lines is called a horizontal zone. ”

“ He should be satisfied with a normal contour, and truthfully assure the patient such hyperinjected contour could not be retained owing to the weight and dropping down of the mass before nature could properly replace it by organized tissue. ”

“ Taking the principle of contrast as applied to pattern design, we can, even within the limited range of black and white and half-tint (as expressed by lines) , get a considerable amount of decorative effect. In the first place by bringing out our pattern, [168] previously outlined, upon a black ground (as in Nos. 1 and 2, p. 169) , increasing the richness of effect, and getting a second plane by treating the lower part in an open tint of line.
Simple contrasts of dark upon light or light upon dark are effective, and sufficient for many purposes, such as borders (as in Nos. 2 and 3, p. 169) . ”

“ The second, that if the contour be observed from a nearer point, or looked at when it is dark against the sky, it will be found composed of millions of minor angles, crags, points, and fissures, which no human sight or hand can draw finely enough, and yet all of which have effect upon the mind. ”

“ Direction of Shade.—On the other hand, if the shading lines, as in Fig. 100, are at the upper left-hand side, then the mind at once grasps the idea of a concave surface.
The first thing, therefore, to keep in mind, is thisp. 97 fact: That in all mechanical drawing, the light is supposed to shine down from the upper left-hand corner and that, as a result, the lower vertical line, as well as the extreme right-hand vertical line, casts the shadows, and should, therefore, be made heavier than the upper horizontal, and the left-hand vertical lines. ”

“ They paint, for example, the head, and shoulders, and cheek of a man, a bust portrait—with a dark background. If you examine the picture closely, you will not find a sharp line, separating the head from the background. In fact the color of the hair and cheek seems to extend a little way into the dark of the background. The artist has dragged his brush round the head, so that it is impossible to say just where the background begins. ”

“ Fig. 34.
Well, as curves are more beautiful than straight lines, it is necessary to a good composition that its continuities of object, mass, or colour should be, if possible, in curves, rather than straight lines or angular ones. Perhaps one of the simplest and prettiest examples of a graceful continuity of this kind is in the line traced at any moment by the corks of a net as it [Pg 370] is being drawn: nearly every person is more or less attracted by the beauty of the dotted line. ”

“ This consequence of a common and yet subsidiary vision of these facets, springs partly from the immobility of the eyes, and partly from the circumstance that only those rays of light which fall in a right line upon a facet of the eye, which itself forms the segment of a circle, can reach the optic nerve of this facet, whereas all others are withheld by the pigment which partly separates the individual glass lenses from each other, and partly surrounds the margin of the chrystalline lens, beneath the cornea. ”

“ The external surface of the lens formed by the aqueous humour and the cornea is not a surface of revolution, such as would be fashioned by a turning lathe or a lens-grinding machine; its curvature is greater in a vertical than in a horizontal direction, and the distinctness of the focussed image is consequently impaired. ”

“ Those formed by the front and base lines of the face constitute the facial angle of the upper part of the face, and indicate the degrees of intellectual and artistic development: those formed by the base-line of the face and the axial line of the neck constitute the facial angle of the lower part of the face, and indicate the degrees of affectional and passional development. ”

“ A space that is arched looks wider than it actually is, for the eye unconsciously follows the lines of the arch, and a distance or width effect is the result. The same space treated with a straight line is quickly bridged. The same space treated with lines that come to an angle looks narrower, for the reason that the eye becomes focused by the apex of the angle, and a height effect, not a breadth effect, is the result. ”

“ Nevertheless, even in women the cosmic laws of Beauty call for a gentle curve instead of a perfectly straight line; but the more subtle the curve the greater is its beauty; whereas the nose itself may be perfectly straight on its upper edge, because it forms a dividing line of the face into two symmetric halves, and by its contrasting straightness heightens the beauty of the surrounding facial curves. ”

“ Let us take a simple example to begin with having directly to do with the use of straight lines in dress. You have probably read a thousand times and heard a hundred times more that stout people must work for straight line effects and the straight line silhouette. But it is one thing to know this fact and another actually to accomplish it in your clothes. You can’t just hang a straight line down from the shoulder like a carpenter’s plumb on a door sill. ”

“ But these colour patches, and the sensations they afford us, are just as often, discontinuous in the highest degree; and the lines constituting a shape may, as for instance in constellations, be entirely imaginary. The fact is that what we feel as a line is not an objective continuity of colour-or-light-patches, but the continuity of our glance's sweep which may either accompany this objective continuity or replace it. ”

“ The vertical division is the more important, as the natural balance is on the lateral sides of a central support. It will be found that the actual centre of the canvas is also the actual pivot or centre of the picture, and around such a point the various components group themselves, pulling and hauling and warring in their claim for attention, the satisfactory picture showing as much design of balance on one side of the centre as the other, and the picture complete in balance displaying this equipoise above and below the horizontal line. ”

“ In the picture of the slit, the place on the cornea of the corneal reflection is shown; and also a minor reflection, which as may be seen traced no curve, from some other source of light. The fine line that crosses the slit horizontally is the image of the thread, above mentioned, which was used in adjusting the head. The time-dots are seen to be perfectly distinct, so that they could be accurately read with the help of a jeweller's eyeglass. ”

“ Fig. 6.
As outlines are composed of profiles, the same laws govern. That the curved line is the line of beauty stands out most evidently in the study of antique designs. Vertical lines and horizontal lines are the lines of support and strength, and must always have proper consideration; but in pure ornament the office of straight lines seems to be confined to connecting curves and to emphasizing their contrasts. ”

“ One morning I fell to sketching a face: what sort of a face it was to be I did not care or know. I took a soft black pencil, gave it a broad point, and worked away. Soon I had traced on the paper a broad and prominent forehead, and a square lower outline of visage: that contour gave me pleasure; my fingers proceeded actively to fill it with features. Strongly marked horizontal eyebrows must be traced under that brow; then followed, naturally, a well-defined nose, with a straight ridge and full nostrils; then a flexible-looking mouth, by no means narrow; ”

“ But when the lines are below the eye, as the floor line and the bureau lines, then they seem to run up to the horizon and are drawn slanting upward; while if they are above the eye, as the top of the mirror, they tip down to the horizon and are drawn slanting downward—the end farther away from the artist lower in the picture than the end nearer him. ”

“ One spot or circumference there should be toward which through the suppression of other parts the eye is led at once. When there, even though the vision has passed far into the canvas, one is at the focal point only, the true goal of the pictorial intention. Any element which proves too attractive along this avenue of entrance is confusing to the sight and weakening to the impression. ”

“ The size of these circles will be either larger or smaller when the principal focus of the eye is either in front of or behind the retina.8
The refractive surfaces of a perfectly formed eye are very like an ellipsoid of revolution with two axes, one of which, the major axis of the ellipse, is at the same time the optic axis and that of rotation; the other is perpendicular to it, and is equal in all meridians. Eyes, however, perfectly constructed are rarely met with. The curvature of the cornea is nearly always greater in one meridian than in another. ”

“ If, therefore, we can by means of lenses or prisms cause the image of any natural object, as seen by the right eye, to be conveyed to the left, and vice versâ, we shall see the relief reversed. A conical cap will appear in relief as a cone, a globe will look like a hollow sphere, and the human face will take the semblance of the inside of a mask. The same deception may be effected by looking at a seal through a short-focused lens, so that the image shall seem reversed. ”

“ If we construct a conical surface touching the body all round, and having its vertex at the luminous point, it is evident that all the space within this surface on the farther side of the opaque body is completely screened from the rays. The cone thus constructed is called the shadow-cone, and its intersection with any surface behind the opaque body defines the shadow cast upon that surface. In the case which we have been supposing—that of a luminous point—the shadow-cone and the shadow itself will be sharply defined. ”

“ The point where the refracted ray cuts the axis, is called by some writers, the centre of the lens; it is within the lens in the cases of double-concave and double-convex lenses, but without, in the meniscus and concavo-convex.
The point is invariably the same at whatever angle the parallel radii be drawn, for
The point where the incident ray cuts the axis is easily found: we have only to put the value of for in the equation, for the single refracting surface, and find
Then
If the thickness of the lens be supposed inconsiderable, may be taken as a straight line, and as one point. ”

“ The kind of line which seems appropriate to representing the delicate edges of a piece of low-relief sculpture, for instance, would require greater force and firmness if we wanted to draw an antique cast in the round, and in strong light and shade. The character of our line should be sympathetic with the character of our subject as far as possible, and sensitive to its differences of character and surface, since it is in this sensitiveness that the expressive power and peculiar virtue of line-drawing consists. ”

“ Lines B4, C3 represent the extreme limits of light that can be received by the cone, and therefore at points 3 and 4 the shadow will commence. The fact that light is reflected to the eye right up to the point 3 does not upset the theory that it can only be reflected from points where the angle of incidence can equal the angle of reflection, as it would seem to do, because the surface being rough presents facets at different angles, from some of which it can be reflected to the eye right up to point 3. ”

“ The surfaces of the lens give back extremely delicate reflections, which with the proper aids may be measured in the living eye, and from the size of which the curve may be calculated as in convex and concave mirrors. ”

“ The CORNEA is the transparent projecting layer, that forms the anterior fifth of the globe of the eye. In form, it is circular, convexo-concave, and resembles a watch-glass. It is received by its edge, which is sharp and thin, within the bevelled border of the sclerotic, to which it is firmly attached. The cornea is composed of several different layers; its blood-vessels are so small that they exclude the red particles altogether, and admit nothing but serum. ”

“ The different degrees of convexity or concavity also modify the refracting character of transparent mediums. The crystalline lens is of different degrees of convexity on its two sides. The convex surfaces of the aqueous and vitreous humors are segments of circles, of different diameters from their concave surfaces. (Fig. 139.) All these 408 circumstances still further influence the refracting character of the visual organ. The achromatic arrangement of the transparent refracting mediums of the eye, remedies the aberration of refraction in the different portions of the eye. ”

“ The compound eye is so delicate and wonderful, that great knowledge of anatomy or the science of optics is necessary before it can be really appreciated. Briefly, it is made up of a cluster of simple eyes, in each of which there are several parts. Beginning at the surface we have what is known as the facet, or cornea, which roughly corresponds to the surface of our own eyes. ”