contour drawing - shows outlines, shapes and edges but not fine detail, texture, tone or colour cross contour drawing - uses lines drawn across surfaces to suggest their depth and form tonal study ...

However, very few of the nearly five dozen sets in NMAH's mathematics collections ... these cases can give us insights into the types of drawing instruments that were valued in engineering practice ...

However, very few of the nearly five dozen sets in NMAH's mathematics collections ... these cases can give us insights into the types of drawing instruments that were valued in engineering practice ...