Page:The Poetry of Architecture.djvu/216

204 a we add another feature, subjected to the same influence, and we increase the general impression of shade; to b we add the same feature, not subjected to this influence, and we have deepened the effect of shade. Now, the principles by which we are to be guided in the selection of one or other of these means are of great importance, and must be developed before we can conclude the investigation of villa architecture. The impression produced by a given effect or influence depends upon its degree and its duration. Degree always moans the proportionate energy exerted. Duration is either into time, or into space, or into both. The duration of colour is in space alone, forming what is commonly called extent. The duration of sound is in space and time; the space being in the size of the waves of air, which give depth to the tone. The duration of mental emotion is in time alone. Now, in all influences, as is the degree, so is the impression; as is the duration, so is the effect of the impression; that is, its permanent operation upon the feelings, or the violence with which it takes possession of our own faculties and senses, as opposed to the abstract impression of its existence without such operation on our own essence. For example, the natural tendency of darkness or shade is, to induce fear or melancholy. Now, as the degree of the shade, so is the