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A no less interesting result of these initial simple operations must, from now on, capture our attention.
We stated from the beginning of this book that Perspective is the foundation of Drawing from Nature. Here, drawing from nature has guided us to the elementary notions of Perspective.
With all our comparisons, by eye and pencil holder, and our experiments that only required string, pins, a sheet of cardboard, a box, it is Perspective that we have practiced, and now we are in a position to understand several terms that, without this preparation, might have intimidated beginners.

ON THE POINT OF VIEW.

First, we can conceive what will henceforth be designated as vanishing lines, since we have just seen that in the faces of the box forming perspective planes, the lines forming the sides of these planes seemed to shorten in our eyes because they were moving away from us, seeming to vanish before us like CE (fig. 6), CH, DF, BE (fig. 10), BC, AD, BF, AE, EG, DG (fig. 13). They will be called vanishing lines, and you must see that, in general, "any line that is neither vertical nor parallel to the observer is a vanishing line."
Now consider that the vanishing lines CE, DF, of the box (fig. 6), seem to approach as they recede from the observer. It is certain that if extended to infinity, they would meet at a point. This point is called the Point of View, and it is of extreme importance in Drawing from Nature, in relation to perspective.
There are still two lines that we need to introduce here. As we will soon be drawing objects in the field, we must be aware of two lines called horizon lines.
The celestial horizon is the line that separates the sky from the earth. The horizon of the eye, or our proper horizon line, is a line parallel to the celestial horizon, and always assumed to be at our eye's height, rising or falling when our eye rises or falls and always stopping at the height where it stops.
Now this Point of View, to which we were led by the vanishing lines, has its place marked on this horizon line we have defined. The Point of View is always the point on the horizon line directly opposite the observer's eye.
Imagine a line originally drawn from the observer's eye to their horizon line: the intersection of these two lines will give the observer's Point of View. Look at your image in a mirror: you can consider your eye reflected by this mirror as your Point of View.

USE OF THE POINT OF VIEW IN DRAWING FROM NATURE.

It will be indispensable in a great number of drawings from nature to know the Point of View we discovered in the previous chapter.
Indeed, all the vanishing lines of objects to be drawn, which, in reality, will be parallel to each other and right-angled to the observer, like the lines CE, DF (fig. 6), and the lines CH, DF, BE (fig. 10), will direct towards the Point of View, so that if sufficiently extended, they would all meet at this point.
An easy observation, which can be repeated daily, can give all possible explanations in this regard.
It has been remarked that by placing oneself at the entrance of a long gallery and fixing the gaze at the other end, one can capture at a glance the entire extent of the gallery, the ceiling remains...

Translation Notes:

"Vanishing lines" refers to lines in perspective drawing that recede towards the vanishing point on the horizon. "Point of view" in this context emphasizes the observer's visual perspective in a drawing.