From certain visual signs, then, the contemplator constructs, muscularly as well as visually, the spatial form of the statue. We have seen that the picture-space is a construction, similarly the statue-space is a construction, and the proportions and relations of the volumes which in this statue-space make up the statue are by no means necessarily the same as those of the mass of marble from which we receive our signs. In other words, the scientific examination of the statue and the imaginative contemplation of it do not yield the same spatial results. Thus the process of measuring[54] statues with a view to discovering a numerical formula for Beauty is little likely to be fruitful. And the work of those, such as Havard Thomas, who have attempted to use this method, show the features which we should expect. Their merits derive from factors outside the range of the theory. The psychological processes involved in the construction of space are too subtle, and the differences between the actual configuration of the marble and the configuration of the statue in the statue-space are brought about in too many ways for any correlation to be established. Among the factors which intervene in the building up of the imaginative form the most obvious are the lighting, and the material. With change of lighting, change of form follows at once through change in the visual signs, and since stone is often a translucent not an opaque material, lighting is by no means such a simple matter as is sometimes supposed. More is involved than the avoidance of distracting cast shadows and the disposal of the brightest illumination upon the right portions of the statue. The general aim should obviously be to reproduce the lighting for which the sculptor designed his work, an aim which requires very sensitive and full appreciation for its success. An aim, moreover, which in the case of works transported from North to South and _vice versa_ is sometimes impossible of realisation.