Let us now consider what will happen, by removing the object beyond the plane passing through =A O B=. In this case the pattern will lose its symmetry from two causes. In the first place, it is manifest, as already explained, that as the eye is necessarily raised a little above the point =E=, and also above the planes =A O E=, =B O E=, it must see through the aperture =A O B= a portion of the object situated below both of these planes. This part of the object will therefore appear to project beyond the point, or below the plane where the direct and reflected images meet. If we suppose, therefore, that all the reflected images were symmetrical, the whole picture would lose its symmetry in consequence of the irregularity of the sector =A O B= seen by direct vision. But this supposition is not correct; for since the image _m n_, Fig. 3, seen by direct vision does not coincide with the first reflected images _mnʹ_, _nmʹ_, it is clear that all the other images will likewise be incoincident, and, therefore, that the figure formed by their combination must lose its symmetry, and, consequently, its beauty. As the eye must necessarily be placed above a line perpendicular to the plane =A B O= at the point =O=, it will see a portion of the object situated below that perpendicular continued to the object. Thus, in Fig. 16, if the eye is placed at _e_ above =E=, and if =M N= is the object placed at the distance =P O=, then the eye at _e_ will observe the portion =P Oʹ= of the object situated below the axis =P O E=, and this portion, which may be called the aberration, will vary with the height =E _e_= of the eye, and with the distance =O P= of the object. [Illustration: FIG. 17.] Let us now suppose =E _e_= and =O P= to be constant, and that a polygonal figure is formed by some line placed at the point =Q= of the object =M N=. Then if =P Q= is very great compared with =P Oʹ=, the polygonal figure will be tolerably regular, though all its angles will exhibit an imperfect junction, and its lower half will be actually, though not very perceptibly, less than its upper half. But if =Q= approaches to =P=, =P Oʹ= remaining the same, so that =P Oʹ= bears a considerable ratio to =P Q=, then the polygonal figure will lose all symmetry, the upper sectors being decidedly the largest, and the lowest sectors the smallest. When =Q= arrives near =P=, the aberration becomes enormous, and the figure is so distorted, that it can no longer be recognised as a polygon.