first edition , 8 pairs of plates, engravings and 'aquatint', last plate loose, title margin little nicked, occasional marking, disbound, 4to, For the Author, sold by Boydell & Austin, 1759. The artist's extremely rare first drawing manual. 'In the two-page explanatory essay he began with a passage from the 1724 English edition of Leonardo da Vinci's Treatise on Painting , which described how invention of composition might be assisted by looking at accidents of nature, such as old walls covered with dirt or streaked stones. Cozens explained that a happy accident with an adept pupil had led him to improve upon Leonardo by creating those imperfect forms on purpose with some degree of design, and then using them as the basis for landscape compositions. These rude black Sketches or blots were drawn swiftly with a brush dipped in Indian ink, from which hints were taken for the outline of a landscape drawn on a clean piece of post paper laid on top. He provided eight pairs of blots and outline landscapes drawn from them as examples of the eight styles of composition, which he listed in the essay, and he intended to exhibit eight finished shaded examples with figures at the shops of the printsellers Boydell and Austin. He engraved the examples himself, employing a unique, very early form of aquatint for the blots.' [Kim Sloan, in ODNB ]