These methods and processes, and the conventionalities of artistic interpretation which maintained themselves through all the changes of taste, have still to be considered. They are the common features by which works which differ greatly in execution are brought into connection, and are to be found as clearly marked in a statue dating from the time of Amasis and Nectanebo as in one from the Ancient Empire. Some of the conventions of Egyptian art are to be explained by the constitution of the human mind and by the conditions under which it works when it attempts plastic reproductions for the first time; others appear to spring from certain habits of thought peculiar to Egyptian civilization. There is yet a third class which must be referred to purely technical causes, such as the capabilities of the materials and tools employed. The influence which these exercised over the artistic expression of thought has been too often underrated. We shall endeavour to recognize their full importance. When we glance at an Egyptian bas-relief, we perceive in it certain imperfections of rendering which we may have often noticed before, either in the early works of other races or in the formless designs which quite young children scribble upon paper. The infancy of art and the art of infancy have much in common. We are accustomed to processes which are scientifically exact. Profiting by the accumulated learning of so many centuries even the school-boy, among us, understands perspective. We are, therefore, apt to feel too much surprise at the awkwardness and inaccuracy which we find in the works of primitive schools, in transcripts produced by man in the presence of nature without any help from the experience of older civilizations. If we wish to do justice to those early artists, we must endeavour to realize the embarrassment which must have been theirs, when they attempted to reproduce upon a flat surface those bodies which offered themselves to their eyes with their three dimensions of height, width, and depth, and with all the complications arising from foreshortening and perspective, from play of light and shade, and from varied colour. Other perplexities must have arisen from the intersection and variety of lines, from the succession of planes, from the necessity for rendering or at least suggesting the thickness of objects! When the desire to imitate natural objects began to make itself felt in man he received his first drawing lesson from the sun. Morning and evening its almost horizontal rays threw his silhouette sharply upon the white rocks and walls, and nothing was easier than to fix the outline of the image thus projected with a piece of charcoal or burnt wood; after this beginning it was easy to imitate such a sun-picture either in large or in small. Such figures were of necessity profiles, as the silhouette given by a head viewed in front would be very uncertain and indistinct.