The text, first published in 1698, was extremely popular. The following quote is from an English translation of 1791.
At our last Assembly you were pleas'd to approve the Design which I then took
to Entertain you upon Expression. It is necessary then in the first place, to
know wherein it Consists.
Expression, in my Opinion, is a Lively and Natural Resemblance of the Things
which we have to Represent: It is a necessary Ingredient in all the parts of
Painting, and without it no Picture can be perfect; it is that which describes
the true Characters of Things; it is by that, the different Natures of Bodies
are distinguished; that the Figures seem to have Motion, and that every thing
therein Counterfeited appears to be Real.
It is as well in the Colouring as in the Design; it ought also to be observed
in the Representation of Landskip, and in the Composition of the Figures.
This, Gentlemen, is what I have endeavoured to make you observe in my past
Discourses; I shall now Essay to make appear to you, that Expression is also a
part which marks the Motions of the Soul, and renders visible the Effects of
Passion.
Admiration
As we have said, that Admiration is the first and most temperate of all the
Passions, wherein the Heart feels the least disturbance, so the Face receives
very little Alteration thereby; and if any, it will be only in the raising of
the Eye-brows, the Ends thereof being yet parallel, the Eye will be a little
more open than ordinary, and the Ball even between the Lids and without Motion,
being fixed on the Object which causes the Admiration. The Mouth will be open,
but will appear without Alteration any more than the other part of the Face.
This Passion produces only a Suspension of Motion, to give time to the Soul to
deliberate what she has to do, and to consider attentively the Object before
her; if that be rare and extraordinary, out of this first and simple Motion of
Admiration is engendred Esteem.
Horror
But if, instead of Scorn, the Object raises Horrour, the Eyebrow will be still
more frowning than in the preceding Action; the Eye-ball instead of being in
the middle of the Eye, will be drawn down to the under Lid; the Mouth will be
open, but closer in the middle than at the corners, which ought to be drawn
back, and by this Action makes Wrinkles in the Cheeks; the Colour of the Visage
will be pale; and the Lips and Eyes something livid; this Action has some
resemblance to Terrour.
Simple Love
The Motions of this Passion, when it is simple, are very soft and simple, for
the Forehead will be smooth, the Eye-balls shall be turned. The Head inclined
towards the Object of the Passion, the Eyes may be moderately open, the White
very lively and shining, and the Eyeball being gently turned towards the
Object, will appear a little sparkling and elevated; the Nose receives no
Alteration, nor any of the parts of the Face; which being only filled with
Spirits, that warm and enliven it, render the Complexion more fresh and lively,
and particularly the Cheeks and Lips; the Mouth must be a little open, the
Corners a little turn'd up, the Lips will appear moist, and this moistness may
be caused by Vapours arising from the Heart.
Laughter
If to Joy succeed Laughter, this Motion is expressed by the Eyebrow raised
about the middle, and drawn down next the Nose, the Eies almost shut; the Mouth
shall appear open, and shew the Teeth; the corners of the Mouth being drawn
back and raised up, will make a wrinkle in the Cheeks, which will appear puffed
up, and almost hiding the Eyes; the Face will be Red, the Nostrils open; and
the Eyes may seem Wet, or drop some Tears, which being very different from
those of Sorrow, make no alteration in the Face; but very much when excited by
Grief.