This section is from the "The elements of drawing & the elements of perspective" book, by J. M. Dent & Sons. Also see Amazon: The Elements Of Drawing & The Elements Of Perspective.
1 It is more difficult, at first, to get, in colour, a narrow gradation than an extended one; but the ultimate difficulty is, as with the pen, to make the gradation go far.
2 Of course, all the columns of colour are to be of equal length.Blue colour, if you can match their colour by any compartment of the crimson or blue in your scales, the grey in the compartment of the grey scale marked with the same number is the grey which must represent that crimson or blue in your light and shade drawing.
Next, prepare scales with gamboge, cobalt and vermilion. You will find that you cannot darken these beyond a certain point1; for yellow and scarlet, so long as they remain yellow and scarlet, cannot approach to black; we cannot have, properly speaking, a dark yellow or dark scarlet. Make your scales of full yellow, blue, and scarlet, half-way down; passing then gradually to white. Afterwards use lake to darken the upper half of the vermilion and gamboge; and Prussian blue to darken the cobalt.
You will thus have three more scales, passing from white nearly to black, through yellow and orange, through sky-blue, and through scarlet. By mixing the gamboge and Prussian blue you may make another with green; mixing the cobalt and lake, another with violet; the sepia alone will make a forcible brown one; and so on, until you have as many scales as you like, passing from black to white through different colours. Then, supposing your scales properly gradated and equally divided, the compartment or degree No. 1. of the grey will represent in chiaroscuro the No. 1. of all the other colours; No. 2. of grey the No. 2. of the other colours, and so on.
It is only necessary, however, in this matter that you should understand the principle; for it would never be possible for you to gradate your scales so truly as to make them practically accurate and serviceable; and even if you could, unless you had about ten thousand scales, and were able to change them faster than ever juggler changed cards, you could
1 The degree of darkness you can reach with the given colour is always indicated by the colour of the solid cake in the box. In a day measure the tints on so much as one side of a frost-bitten apple: but when once you fully understand the principle, and see how all colours contain as it were a certain quantity of darkness, or power of dark relief from white - some more, some less; and how this pitch or power of each may be represented by equivalent values of grey, you will soon be able to arrive shrewdly at an approximation by a glance of the eye, without any measuring scale at all.
You must now go on, again with the pen, drawing patterns, and any shapes of shade that you think pretty, as veinings in marble or tortoiseshell, spots in surfaces of shells, c, as tenderly as you can, in the darknesses that correspond to their colours; and when you find you can do this successfully, it is time to begin rounding.
Go out into your garden, or into the road, and pick up the first round or oval stone you can find, not very white, not very dark; and the smoother it is the better, only it must not shine. Draw your table near the window, and put the stone, which I will suppose is about the size of a in Fig. 5. (it had better not be much larger), on a piece of not very white paper, on the table in front of you. Sit so that the light may come from your left, else the shadow of the pencil point interferes with your sight of your work. You must not let the sun fall on the stone, but only ordinary light: therefore choose a window which the sun does not come in at. If you can shut the shutters of the other windows in the room it will be all the better; but this is not of much consequence.
Now, if you can draw that stone, you can draw anything: I mean, anything that is drawable. Many things (sea foam, for instance) cannot be drawn at all,only the idea of them more or less suggested; but if you can draw the stone rightly, everything within reach of art is also within yours.
For all drawing depends, primarily, on your power of representing Roundness. If you can once do that, all the rest is easy and straightforward; if you cannot do that, nothing else that you may be able to do will be of any use. For Nature is all made up of roundnesses; not the roundness of perfect globes, but of variously curved surfaces. Boughs are rounded, leaves are rounded,stones are rounded,clouds are rounded, cheeks are rounded, and curls are rounded: there is no more flatness in the natural world than there is vacancy. The world itself is round, and so is all that is in it, more or less, except human work, which is often very flat indeed.
Therefore, set yourself steadily to conquer that round stone, and you have won the battle.
Look your stone antagonist boldly in the face. You will see that the side of it next the window is lighter than most of the paper; that the side of it farthest from the window is darker than the paper; and that the light passes into the dark gradually, while a shadow is thrown to the right on the paper itself by the stone: the general appearance of things being more or less as in a, Fig. 5., the spots on the stone excepted, of which more presently.