|Vol 13||APRIL, 1911.||Nee 1|
|Copyright, 1911, door HW PERCIVAL.|
HOW mysterious and commonplace a thing is a shadow. Shadows perplex us as infants in our early experiences in this world; shadows accompany us in our walks through life; and shadows are present when we depart this world. Our experience with shadows begins soon after we have come into the world’s atmosphere and have seen the earth. Although we soon manage to convince ourselves that we know what shadows are, yet few of us have examined them closely enough.
As infants we have lain in our cribs and watched and wondered at shadows thrown on the ceiling or the wall by persons moving in the room. Those shadows were strange and mysterious, until we had solved the problem to our infant minds by discovering that the movement of a shadow depended on the movement of the person whose outline and shadow it was, or on the movement of light which made it visible. Still it required observation and reflection to discover that a shadow was largest when nearest to the light and farthest from the wall, and that it was smallest and least formidable when farthest from the light and nearest to the wall. Later, as children, we were entertained by the rabbits, geese, goats, and other shadows which some friend produced by skillful manipulation of his hands. As we grew older, we were no longer entertained by such shadow play. Shadows are still strange, and the mysteries surrounding them will remain until we know the different kinds of shadows; what shadows are, and what they are for.
The shadow lessons of childhood teach us two of the laws of shadows. The movement and changing of shadows on their field vary with the light by which they are seen and with the objects the outlines and shadows of which they are. Shadows are large or small as those who throw them are far from or near to the field on which shadows are perceived.
We may have now forgotten these facts as we forget many of the important lessons of childhood; but, if they were then learned, their importance and truth will appeal to us in later days, when we shall know that our shadows have changed.
There are, we may at present say, four factors necessary for the casting of a shadow: First, the object or thing which stands in; second, the light, which makes visible; third, the shadow; and, fourth, the field or screen on which the shadow is seen. This seems easy enough. When we are told that a shadow is merely the outline on a surface of any opaque object which intercepts the rays of light falling on that surface, the explanation seems so simple and easily understood as to make further inquiry unnecessary. But such explanations, true though they may be, do not altogether satisfy the senses nor the understanding. A shadow has certain physical characteristics. A shadow is more than a mere outline of an object which intercepts the light. It produces certain effects on the senses and it affects the mind strangely.
All bodies which are called opaque will cause a shadow to be thrown when they stand before the source from which light comes; but the nature of a shadow and the effects which it produces differ according to the light which projects the shadow. The shadows thrown by sunlight and their effects are different than shadows caused by the light of the moon. The light of the stars produces a different effect. The shadows thrown by lamp, gas, electric light or by any other artificial source are different as to their natures, though the only difference which appears to the sight is the greater or lesser distinctness in the outline of the object on the surface on which the shadow is thrown.
No physical object is opaque in the sense that it is impervious to or intercepts all light. Each physical body intercepts or cuts off some of the rays of the light and transmits or is transparent to other rays.
A shadow is not merely the absence of the light in the outline of the object which intercepts it. A shadow is a thing in itself. A shadow is something more than a silhouette. A shadow is more than the absence of light. A shadow is the projection of an object in combination with the light by which it is projected. A shadow is the projection of the copy, counterpart, double, or ghost of the projected object. There is a fifth factor necessary for the causing of a shadow. The fifth factor is the shade.
When we look at a shadow we see the outline of the object projected, on a surface which intercepts the shade. But we do not see the shade. The actual shade and the actual shadow are not mere outlines. The shadow is a projection of the shade of the interior as well as of the outline of the body. The interior of the body cannot be seen because the eye is not sensible to the rays of light which comingles with the interior of the body and projects its shade. All of the shade or shadow that can be perceived through the eye is the outline of light only, to which the eye is sensible. But if the sight were trained, the seer could perceive the interior of the body in all its parts by means of its shade, because the light that passes through the body is impressed with and bears a subtle copy of the parts of the body through which it passes. The physical surface on which the shadow is seen, that is to say, which causes the outline of the light in the form of the body to be seen, has impressed upon it a copy of the shade, and is affected by the shadow to the degree that it retains the impression long after the body or light which throws it is removed.
If the surface of a plate were sensitized to the rays of light which pass through bodies called opaque and which throw a shadow, this surface would retain the impression or shadow, and it would be possible for one with trained sight to see not only the outline of the figure, but to describe and analyze the interior of the original of that shadow. It would be possible to diagnose the condition of the living body at the time of the shadow impression and to predict future states of illness or health according to the diagnosis. But no plate or surface does retain the impress of the shadow as it is seen by ordinary physical sight. That which is called a shadow, from the physical standpoint, produces certain effects, but these are not seen.