The sight of some landscape wakens in the beholder a vivid and definite emotion; he is moved by it to some form of expression. If he is a painter he will express his emotion by means of a picture, which involves in the making of it certain elements and certain processes. The picture will present selected facts in the landscape; the landscape, then, as constructed according to the design the painter has conceived of it, becomes the motive or subject of his picture. The particular aspects of the landscape which the picture records are its color and its form. These qualities of color and form are the painter's medium. An etching of the scene would use not color but line to express the artist's emotion in its presence; so line is the medium of etching. But "qualities" of objects are an abstraction unless they are embodied in material. In order, therefore, to give his medium actual embodiment the painter uses pigment, as oil-color or water-color or tempera, laid upon a surface, as canvas, wood, paper, plaster; this material pigment is his vehicle. The etcher employs inked scratches upon his plate of zinc or copper, bitten by acid or scratched directly by the needle; these marks of ink are the vehicle of etching. To the way in which the artist uses his medium for practical expression and to his methods in the actual handling of his vehicle is applied the term technique. The general conception of his picture, its total design, the choice of motive, the selection of details, the main scheme of composition,--these belong to the great strategy of his art. The application of these principles in practice and their material working out upon his canvas are an affair of tactics and fall within the province of technique.