Architectural drawings are drawn to scale, that of eight feet to one inch being general, with working drawings to a scale of half an inch to the foot accompanied by full-size details and profiles of mouldings. The drawings are geometric, that is in plan, elevation, and section, expressed in line and generally tinted. On plans and sections arbitrary colours are employed to indicate material, for instance, red denotes brick, purple-grey, stone, warm grey, cement, Prussian blue, iron or steel, and burnt sienna or Vandyke brown, wood. These drawings convey little idea of the intended effect to the lay mind, and it is customary to suggest the eventual appearance by perspective views, but for practical reasons they constitute the most convenient form from which dimensions can be taken for working purposes. _Structural Design_ In all structural design similar drawings are necessary, although sketch designs in perspective may be made to suggest effect, working drawings are imperative to the execution of the work. These, when reduced to the essential conditions of rendering, with explanatory details and sections, assume a very different aspect to the original sketch. The success of the completed work depends upon skilful detailing, which must be thoroughly explicit to be of real value. For convenience such working drawings are generally made on detail paper, which is usually obtainable in rolls sixty inches wide by twenty-five or fifty yards. This is sufficiently transparent to be employed for tracings, a great convenience when copies are in request, and is a good surface for pen, pencil or chalk, though somewhat thin for colour. Designs can be sketched in charcoal, and the desired lines drawn in ink. When dry the charcoal lines can be obliterated by rubbing with a leather or soft cloth, by which the charcoal is distributed, forming a tone over the whole surface. This is easily removable by india-rubber, and excellent relief effects can be obtained by judiciously taking out lights and strengthening shadows, though to avoid any possible misunderstanding it is usual to also indicate the relief by sections drawn through the details. _Lucid Arrangement_ In geometric and working drawings when plans and sections are incidental to lucid explanation, these latter should appear relatively; that is, the plan should be in alignment with the elevation, etc. Statements and directions as to procedure are often necessary, and these, placed with judgment and in good lettering, are valuable in balancing the drawing. Not that this has any effect on the work, but because it has a good influence on the designer. Possibly the story of Giotto and the circle that figured in the early school primers is responsible for the very general impression that the use of mechanical instruments is inartistic. Another characteristic of the young beginner is a total disregard for anything in the nature of exact dimension.