§ 3. If ever I am able to understand the process of the cumulus formation,[1] it will become to me one of the most interesting of all subjects of study to trace the connection of the threatening and terrible outlines of thunder-cloud with the increased action of the electric power. I am for the present utterly unable to speak respecting this matter, and must pass it by, in all humility, to say what little I have ascertained respecting the more broken and rapidly moving forms of the central clouds, which connect themselves with mountains, and may, therefore, among mountains, be seen close and truly. § 4. Yet even of these, I can only reason with great doubt and continual pause. This last volume ought certainly to be better than the first of the series, for two reasons. I have learned, during the sixteen years, to say little where I said much, and to see difficulties where I saw none. And I am in a great state of marvel in looking back to my first account of clouds, not only at myself, but even at my dear master, M. de Saussure. To think that both of us should have looked at drifting mountain clouds, for years together, and been content with the theory which you will find set forth in § 4, of the chapter on the central cloud region (Vol. I.), respecting the action of the snowy summits and watery vapor passing them. It is quite true that this action takes place, and that the said fourth paragraph is right, as far as it reaches. But both Saussure and I ought to have known--we both did know, but did not think of it--that the covering or cap-cloud forms on hot summits as well as cold ones;--that the red and bare rocks of Mont Pilate, hotter, certainly, after a day's sunshine than the cold storm-wind which sweeps to them from the Alps, nevertheless have been renowned for their helmet of cloud, ever since the Romans watched the cloven summit, gray against the south, from the ramparts of Vindonissa, giving it the name from which the good Catholics of Lucerne have warped out their favorite piece of terrific sacred biography.[2] And both my master and I should also have reflected, that if our theory about its formation had been generally true, the helmet cloud ought to form on every cold summit, at the approach of rain, in approximating proportions to the bulk of the glaciers; which is so far from being the case that not only (A) the cap-cloud may often be seen on lower summits of grass or rock, while the higher ones are splendidly clear (which may be accounted for by supposing the wind containing the moisture not to have risen so high), but (B) the cap-cloud always shows a preference for hills of a conical form, such as the Mole or Niesen, which can have very little power in chilling the air, even supposing they were cold themselves, while it will entirely refuse to form round huge masses of mountain, which, supposing them of chilly temperament, must have discomforted the atmosphere in their neighborhood for leagues. And