It is not only when we try to speculate about Deity that we find ourselves encompassed with difficulties and are made to realize how very short is our mental tether in some directions. This world, in its commonest aspects, presents many baffling problems, of which it is sometimes wholesome that we should be reminded. If you look at a piece of iron, it seems solid; it looks as if its particles must be everywhere in contact with one another. And yet, by hammering, or by great pressure, or by intense cold, the piece of iron may be compressed, so that it will occupy less space than before. Evidently, then, its particles are not in contact, but are separated from one another by unoccupied tracts of enveloping space. In point of fact, these particles are atoms arranged after a complicated fashion in clusters known as molecules. The word _atom_ means something that cannot be cut. Now, are these iron atoms divisible or indivisible? If they are divisible, then what of the parts into which each one can be divided; are they also divisible? and so on forever. But if these iron atoms are indivisible, how can we conceive such a thing? Can we imagine two sides so close together that no plane of cleavage could pass between them? Can we imagine cohesive tenacity too great to be overcome by any assignable disruptive force, and therefore infinite? Suppose, now, we heat this piece of iron to a white heat. Scientific inquiry has revealed the fact that its atom-clusters are floating in an ocean of ether, in which are also floating the atom-clusters of other bodies and of the air about us. The heating is the increase of wave motion in this ether, until presently a secondary series of intensely rapid waves appear as white light. Now this ether would seem to be of infinite rarity, since it does not affect the weight of bodies, and yet its wave-motions imply an elasticity far greater than that of coiled steel. How can we imagine such powerful resilience combined with such extreme tenuity?