point—the vanishing point which lies on the horizon, this being the height of the camera lens.
The pictures on the far wall exactly face the spectator, therefore they do not diminish.
You were told to lay the thread first on the floor, then on the ceiling. This is always the wisest plan. If you find the boundary lines correctly, then all within those lines falls into place.
When you are drawing from Nature always check the outside lines. If sketching the whole of the house, find the top line of the roof, and the base of the walls; then the rest of the roof, the windows, doorways, lintel, and porch will all fall into place and save you an enormous amount of needless bother. If the outside lines are correct, then it stands to reason that everything within those lines will agree.
It matters not whether it is only a box or a house, a barn or a chair, a boat or a book—always, always check the extreme limit.
By the very simple aid of a thread you can discover many things. You can trace the low horizon of pictures that represent the low-lying ground. You will also discover that the low horizon gives ample space for the sky, and that clouds also conform to the laws of perspective and disappear as they recede.
Pictures of interiors of houses are extremely interesting. There you note that the walls, floor, and ceiling (or rafters of the roof) diminish to the same vanishing point (because they lie parallel one to another), but that the chairs and tables, unless they are arranged parallel with the walls, have each a separate vanishing point, though each vanishing point must, of necessity, meet on the same horizon. (See Fig. 53)
By making a friend of perspective and interesting ourselves in its various little problems, looking not only for the perspective in our own drawings, but for the perspective in others, we shall soon acquire a useful amount of knowledge.
