But even in the merely general equability of distribution, as regards the atoms, there appears a difficulty which, no doubt, has already suggested itself to those among my readers who have borne in mind that I suppose this equability of distribution effected through _irradiation from a centre_. The very first glance at the idea, irradiation, forces us to the entertainment of the hitherto unseparated and seemingly inseparable idea of agglomeration about a centre, with dispersion as we recede from it—the idea, in a word, of _in_equability of distribution in respect to the matter irradiated. Now, I have elsewhere[1] observed that it is by just such difficulties as the one now in question—such roughnesses—such peculiarities—such protuberances above the plane of the ordinary—that Reason feels her way, if at all, in her search for the True. By the difficulty—the “peculiarity”—now presented, I leap at once to _the_ secret—a secret which I might never have attained _but_ for the peculiarity and the inferences which, _in its mere character of peculiarity_, it affords me. [1] “_Murders in the Rue Morgue_”—p. 133. The process of thought, at this point, may be thus roughly sketched:—I say to myself—“Unity, as I have explained it, is a truth—I feel it. Diffusion is a truth—I see it. Irradiation, by which alone these two truths are reconciled, is a consequent truth—I perceive it. _Equability_ of diffusion, first deduced _à priori_ and then corroborated by the inspection of phænomena, is also a truth—I fully admit it. So far all is clear around me:—there are no clouds behind which _the_ secret—the great secret of the gravitating _modus operandi_—can possibly lie hidden;—but this secret lies _hereabouts_, most assuredly; and _were_ there but a cloud in view, I should be driven to suspicion of that cloud.” And now, just as I say this, there actually comes a cloud into view. This cloud is the seeming impossibility of reconciling my truth, _irradiation_, with my truth, _equability of diffusion_. I say now:—“Behind this _seeming_ impossibility is to be found what I desire.” I do not say “_real_ impossibility;” for invincible faith in my truths assures me that it is a mere difficulty after all—but I go on to say, with unflinching confidence, that, _when_ this _difficulty_ shall be solved, we shall find, _wrapped up in the process of solution_, the key to the secret at which we aim. Moreover—I _feel_ that we shall discover _but one_ possible solution of the difficulty; this for the reason that, were there two, one would be supererogatory—would be fruitless—would be empty—would contain no key—since no duplicate key can be needed to any secret of Nature.