These efforts to realise the unrealisable make one's head swim; let us hark back once more from cosmical time to the puny bigness of our earthly animals, living or extinct. If we look at the whole of our existing fauna, marine and terrestrial, we shall soon see that we could bring together at the present moment a very goodly collection of extant monsters, most parlous monsters, too, each about as fairly big in its own kind as almost anything that has ever preceded it. Every age has its own _specialite_ in the way of bigness; in one epoch it is the lizards that take suddenly to developing overgrown creatures, the monarchs of creation in their little day; in another, it is the fishes that blossom out unexpectedly into Titanic proportions; in a third, it is the sloths or the proboscideans that wax fat and kick with gigantic members; in a fourth, it may be the birds or the men that are destined to evolve with future ages into veritable rocs or purely realistic Gargantuas or Brobdingnagians. The present period is most undoubtedly the period of the cetaceans; and the future geologist who goes hunting for dry bones among the ooze of the Atlantic, now known to us only by the scanty dredgings of our 'Alerts' and 'Challengers,' but then upheaved into snow-clad Alps or vine-covered Apennines, will doubtless stand aghast at the huge skeletons of our whales and our razorbacks, and will mutter to himself in awe-struck astonishment, in the exact words of my friend at South Kensington, 'Things used all to be so very big in those days, usedn't they?'