Altho' the instances already given are pretty flagrant, yet it is certainly true, (as a farther confirmation of this, and for the consolation of those, who may be a little piqued at what has been said) that painters of every condition are stronger instances of the almost unavoidable power of prejudice, than any people whatever.
What are all the manners, as they are call'd, of even the greatest masters, which are known to differ so much from one another, and all of them from nature, but so many strong proofs of their inviolable attachment to falshood, converted into establish'd truth in their own eyes, by self-opinion? Rubens would, in all probability, have been as much disgusted at the dry manner of Poussin, as Poussin was at the extravagant of Rubens. The prejudices of inferior proficients in favour of the imperfections of their own performances, is still more amazing.——Their eyes are so quick in discerning the faults of others, at the same time they are so totally blind to their own! Indeed it would be well for us all, if one of Gulliver's flappers could be placed at our elbows to remind us at every stroke how much prejudice and self-opinion perverts our sight.
From what has been said, I hope it appears that those, who have no bias of any kind, either from their own practice, or the lessons of others, are fittest to examine into the truth of the principles laid down in the following pages. But as every one may not have had an opportunity of being sufficiently acquainted with the instances, that have been given: I will offer one of a familiar kind, which may be a hint for their observing a thousand more. How gradually does the eye grow reconciled even to a disagreeable dress, as it becomes more and more the fashion, and how soon return to its dislike of it, when it is left off, and a new one has taken possession of the mind?—so vague is taste, when it has no solid principles for its foundation!
Notwithstanding I have told you my design of considering minutely the variety of lines, which serve to raise the ideas of bodies in the mind, and which are undoubtedly to be consider'd as drawn on the surfaces only of solid or opake bodies: yet the endeavouring to conceive, as accurate an idea as is possible, of the inside of those surfaces, if I may be allow'd the expression, will be a great assistance to us in the pursuance of our present enquiry.
In order to my being well understood, let every object under our consideration, be imagined to have its inward contents scoop'd out so nicely, as to have nothing of it left but a thin shell, exactly corresponding both in its inner and outer surface, to the shape of the object itself: and let us likewise suppose this thin shell to be made up of very fine threads, closely connected together, and equally perceptible, whether the eye is supposed to observe them from without, or within; and we shall find the ideas of the two surfaces of this shell will naturally coincide. The very word, shell, makes us seem to see both surfaces alike.
The use of this conceit, as it may be call'd by some, will be seen to be very great, in the process of this work: and the oftner we think of objects in this shell-like manner, we shall facilitate and strengthen our conception of any particular part of the surface of an object we are viewing, by acquiring thereby a more perfect knowledge of the whole, to which it belongs: because the imagination will naturally enter into the vacant space within this shell, and there at once, as from a center, view the whole form within, and mark the opposite corresponding parts so strongly, as to retain the idea of the whole, and make us masters of the meaning of every view of the object, as we walk round it, and view it from without.
Thus the most perfect idea we can possibly acquire of a sphere, is by conceiving an infinite number of straight rays of equal lengths, issuing from the center, as from the eye, spreading every way alike; and circumscribed or wound about at their other extremities with close connected circular threads, or lines, forming a true spherical shell.
But in the common way of taking the view of any opake object, that part of its surface, which fronts the eye, is apt to occupy the mind alone, and the opposite, nay even every other part of it whatever, is left unthought of at that time: and the least motion we make to reconnoitre any other side of the object, confounds our first idea, for want of the connexion of the two ideas, which the complete knowledge of the whole would naturally have given us, if we had considered it in the other way before.
Another advantage of considering objects thus merely as shells composed of lines, is, that by these means we obtain the true and full idea of what is call'd the out-lines of a figure, which has been confin'd within too narrow limits, by taking it only from drawings on paper; for in the example of the sphere given above, every one of the imaginary circular threads has a right to be consider'd as an out-line of the sphere, as well as those which divide the half, that is seen, from that which is not seen; and if the eye be supposed to move regularly round it, these threads will each of them as regularly succeed one another in the office of out-lines, (in the narrow and limited sense of the word:) and the instant any one of these threads, during this motion of the eye, comes into sight on one side, its opposite thread is lost, and disappears on the other. He who will thus take the pains of acquiring perfect ideas of the distances, bearings, and oppositions of several material points and lines in the surfaces of even the most irregular figures, will gradually arrive at the knack of recalling them into his mind when the objects themselves are not before him: and they will be as strong and perfect as those of the most plain and regular forms, such as cubes and spheres; and will be of infinite service to those who invent and draw from fancy, as well as enable those to be more correct who draw from the life.
In this manner, therefore, I would desire the reader to assist his imagination as much as possible, in considering every object, as if his eye were placed within it. As straight lines are easily conceiv'd, the difficulty of following this method in the most simple and regular forms will be less than may be first imagined; and its use in the more compounded will be greater: as will be more fully shewn when we come to speak of composition.
But as [Fig. 2 L p. I] may be of singular use to young designers in the study of the human form, the most complex and beautiful of all, in shewing them a mechanical way of gaining the opposite points in its surface, which never can be seen in one and the same view; it will be proper to explain the design of it in this place, as it may at the same time add some weight to what has been already said.
It represents the trunk of a figure cast in soft wax, with one wire pass'd perpendicularly through its center, another perpendicularly to the first, going in before and coming out in the middle of the back, and as many more as may be thought necessary, parallel to and at equal distances from these, and each other; as is mark'd by the several dots in the figure.—Let these wires be so loose as to be taken out at pleasure, but not before all the parts of them, which appear out of the wax, are carefully painted close up to the wax, of a different colour from those, that lie within it. By these means the horizontal and perpendicular contents of these parts of the body (by which I mean the distances of opposite points in the surface of these parts) through which the wires have pass'd, may be exactly known and compared with each other; and the little holes, where the wires have pierced the wax, remaining on its surface, will mark out the corresponding opposite points on the external muscles of the body; as well as assist and guide us to a readier conception of all the intervening parts. These points may be mark'd upon a marble figure with calibers properly used.
The known method, many years made use of, for the more exactly and expeditiously reducing drawings from large pictures, for engravings; or for enlarging designs, for painting cielings and cupolas, (by striking lines perpendicular to each other, so as to make an equal number of squares on the paper design'd