Old White would say "that he should not wonder if our descendants got outside the world altogether, and voyaged far and away upon the Ether ocean."—Author, chap. i.
I offer here, in the first place, just a few preliminary reflections on the scientific retrospect. Although our nineteenth century scientists, especially towards the end of the century, are reputed to have thought themselves very acute, and the progress of their time very rapid and striking, yet, in looking back, and after all due allowances, one is impressed by the dulness of mental grasp about that time, even where there had already been reached many of those elementary facts which have since served us so well as leverage for further steps of science-progress. Take, for instance, the electro-light speed, which, after all, is simply proportionate to speed of ordinary light as compared to speed of sound, both of the latter being facts perfectly well known of old. Then, again, the electro-light speed once determined, we were already halfway
