What am I supposed to do with these reference images?

Question

I'm drawing from the book Julien's studies of heads: selected from paintings of eminent artists, or drawn from nature (link).

When a page shows two drawings: one being a rough outline with a cross through it to show proportions, and next to it another drawing of the same subject but detailed in and with no cross through it, am I meant to

1. draw the first one with a cross as an aid, and then draw the 2nd one without a cross, or

2. draw the first one with a cross and then use the details from the 2nd image to flesh it out, and then erase the cross?

^{Example from p. 52 of the cited and linked book}

Answer 1

It depends.

It depends on what you are wanting to do with the drawing. If you are doing mockups or brainstorming ideas, the cross through drawing will be left there. If you are doing a quick sketch before you progress on your overall piece of art. You would lightly draw in the casting shapes and erase them once you have the overall image mapped out. You could also use the light outline and then blend it in with a tortillon or a blending stump.

I don't think there is a right or a wrong way of using them. But for beginner artists it would be suggested to use the outlines to understand how objects face to understand perspective.

Regarding the link you posted in the comments. The beginning artist will want to use a grid method to understand the exact points (the cross reference) to get your eyes to understand how far each point is drawn. The third eye in the image shows a singular line drawn across. Showing a less grid-like pattern so you are able to look at the distance between the single line, and notice the difference between the bottom and upper eye lid. Also the distance between the pupil and iris.

Example:

Source: https://archive.org/details/gri_33125008674232/page/n11/mode/2up

Answer 2

Some excerpts (rather one half, emphases by me) from the introduction to the book by Thomas Fairland, in which the usefulness of the images is made clear:

The system endeavoured to be illustrated in the accompanying Plates, by a progressive course of figures, is that essential method of decidedly determining the relative bearings of all the most conspicuous points in a geometrical manner, before proceeding with details, as is indicated in the early examples by dotted lines; nothing is arranged or recommended in the copying of the present subjects, but upon principles which can be equally and truly applied to the delineation of the real objects, and therefore the learner may rely with certainty on the foundation these will become for subsequent practice.

Having mastered [the single features of the face], the full face may then occupy his attention; and in this a few mechanical rules will assist him: as, for instance, in attempting the entire face he may first describe an oval, somewhat narrower towards the bottom than at the top, when he is at liberty to draw, or suppose to be drawn, a perpendicular line down the middle, which serves as a guide for the situation of the nose and mouth ; this line is to be crossed by others, on which are placed the nostrils, mouth, and chin. In every variety of position the existence or supposition of these lines is of great service to the learner, as they enable him to place the features much more accurately than could be done without an adherence to them; always remembering that in every case the lines on -which the eyes, nostrils, mouth, and chin are placed, must perfectly correspond with each other, and be always at right angles -with the perpendicular line supposed to be drawn through their centre: the continuance of this method will more readily produce accuracy, and undoubtedly render the practice more easy and agreeable to the beginner.

In other words, the reference lines are there to get a feeling for the relative proportions, directions, and volumes, and can be used both as physical guides in your drawings or as purely visual aids.