rence of catastrophe and convulsion may be part and parcel of uniformity itself; and so in like manner, when the speculations of Darwin have furnished the mechanists with renewed passion for a new doll, Prof. Huxley has hoisted more than once a caution signal. He has uttered a warning voice against converting a scientific hypothesis into a dogmatic creed.
It was high time. The passionate enthusiasm with which an obscure and confused verbal metaphor has been accepted as solving all the mysteries involved in the origin of new forms of organic life, will one day be seen to have been—what it is—only another great warning example of the impediments which beset the progress of knowledge. That the origin of species may be ascribed to some thing called "Nature" selecting things which did not as yet exist, and could not therefore have been presented for selection, is among those mysteries of nonsense which are not uncommon in the history of the human mind. But even this delusion, prevalent as it has been, is breaking down, and assaults upon it, all too timid though they be, are nevertheless increasing day by day. I have therefore much sympathy with those who on the whole are reasonably proud of geology as regards its past, and are reasonably hopeful of it as regards its future. But its progress, and even our appreciation of its present teaching, is absolutely dependent on two conditions: first, that we bear constantly in mind the wide seas of ignorance which surround the little islands of our knowledge; and, secondly, that we rightly estimate the full sweep and significance of the facts and laws which we can clearly see. It would be difficult to say whether the science has suffered most from forgetfulness of the things that we do not know, or from failure to appreciate or exhaust the consequences flowing from the things we do know. The vision of past worlds which geology presents may be compared to the view of some land seen at a distance upon the ocean, and upon which heavy banks of cloud are resting. Above, mountains and peaks are seen here and there, with outlines cut clear against the sky. Below, capes and headlands and promontories are also seen, cut as clearly against the sea. The middle slopes are only visible at intervals, and some great plains just roughen the verge of the horizon. But all details are lost. We do not even know whether we are looking at one continuous land or at a group of islands. Hills which seem united, or separated only by some narrow valley, may be really far apart, and broad channels of the deepest water may lie between them. So it is with the vast landscapes of the past in the revelations of geology. The general outlines of geological causation are clear enough; and so in broad outline, too, is the general succession of organic life. But both the exact history of the rocks, and the exact history of the creatures which they entomb, are
