tions, and just as overwhelming in their myriads as are those which lie within that one particular sphere of which alone we know anything with certainty.
Provided with this conception, we see at once that the doctrine of a visible central sun is an absurdity. As to whether there may be some central sun somewhere or other I can express no opinion, save that I do not see any reason whatever to think that such a body should exist. But we may feel practically certain, according to all rational grounds of probability, that even if there were a central sun in the universe it would not lie within our ken. Suppose that in the wide extent of the Atlantic Ocean there was one individual diatom of a specially interesting character; I do not mean one species with its myriad individuals, but one solitary specimen of a particular microscopic organism, which happened to flourish somewhere or other in the North or South Atlantic Ocean at some depth or other from the surface. Supposing that absolutely nothing further was known as to the whereabouts of this individual object; it might, for anything we could tell, lie beneath a mighty ice-floe in the Arctic regions; it might be miles deep in the Caribbean Sea; it might be basking on the surface in the Equatorial calms; it might be tossed in the surf on the shores of St. Helena; it might be floating at the mouth of the Amazons; it might be off the Cape of Good Hope, or amid the Antarctic icebergs. Would any reasonable man who desired to obtain that unique and extraordinary specimen for his collection imagine that if he went down to the coast of Cornwall and lifted a single drop from the Atlantic he would have such inconceivably good fortune as to find in it this rare diatom of which but a single individual existed through-
