From the above facts it would seem that certain bodies have the power of imbibing light and again emitting it, in certain circumstances, and that this power may remain for a considerable length of time. It is observed that the light which such bodies emit bears an analogy to that which they have imbibed. In general, the illuminated phosphorus is reddish; but when a weak light only has been admitted to it, or when it has been received through pieces of white paper, the emitted light is pale or whitish.--Mr. Morgan, in the seventy-fifth volume of the Philosophical Transactions, treats the subject of light at considerable length; and as a foundation for his reasoning, he assumes the following data:--1. That light is a body, and like all others, subject to the laws of attraction. 2. That light is a heterogeneous body; and that the same attractive power operates with different degrees of force on its different parts. To the principle of attraction, likewise, Sir Isaac Newton has referred the most extraordinary phenomena of light, Refraction and Inflection. He has also endeavoured to show that light is not only subject to the law of attraction but of repulsion also, since it is repelled or reflected from certain bodies. If such principles be admitted, then, it is highly probable that the phosphorescent bodies to which we have adverted have a power of attracting or imbibing the substance of light, and of retaining or giving it out under certain circumstances, and that the matter of light is incorporated at least with the surface of such bodies. But on this subject, as on many others, there is a difference of opinion among philosophers.[5]