But when the moon, having passed the line of pinnacles, was hidden behind the stupendous white swell of Mont Blanc, the masterpiece of the evening was flung on the canvas.  A rich greenish radiance sprang into the sky from behind the mountain, and in this same airy shreds and ribbons of vapor floated about, and being flushed with that strange tint, went waving to and fro like pale green flames.  After a while, radiating bars—­vast broadening fan-shaped shadows—­grew up and stretched away to the zenith from behind the mountain.  It was a spectacle to take one’s breath, for the wonder of it, and the sublimity.

Indeed, those mighty bars of alternate light and shadow streaming up from behind that dark and prodigious form and occupying the half of the dull and opaque heavens, was the most imposing and impressive marvel I had ever looked upon.  There is no simile for it, for nothing is like it.  If a child had asked me what it was, I should have said, “Humble yourself, in this presence, it is the glory flowing from the hidden head of the Creator.”  One falls shorter of the truth than that, sometimes, in trying to explain mysteries to the little people.  I could have found out the cause of this awe-compelling miracle by inquiring, for it is not infrequent at Mont Blanc,—­but I did not wish to know.  We have not the reverent feeling for the rainbow that a savage has, because we know how it is made.  We have lost as much as we gained by prying into the matter.

We took a walk down street, a block or two, and a place where four streets met and the principal shops were clustered, found the groups of men in the roadway thicker than ever—­for this was the Exchange of Chamonix.  These men were in the costumes of guides and porters, and were there to be hired.

The office of that great personage, the Guide-in-Chief of the Chamonix Guild of Guides, was near by.  This guild is a close corporation, and is governed by strict laws.  There are many excursion routes, some dangerous and some not, some that can be made safely without a guide, and some that cannot.  The bureau determines these things.  Where it decides that a guide is necessary, you are forbidden to go without one.  Neither are you allowed to be a victim of extortion:  the law states what you are to pay.  The guides serve in rotation; you cannot select the man who is to take your life into his hands, you must take the worst in the lot, if it is his turn.  A guide’s fee ranges all the way up from a half-dollar (for some trifling excursion of a few rods) to twenty dollars, according to the distance traversed and the nature of the ground.  A guide’s fee for taking a person to the summit of Mont Blanc and back, is twenty dollars—­and he earns it.  The time employed is usually three days, and there is enough early rising in it to make a man far more “healthy and wealthy and wise” than any one man has any right to be.  The porter’s fee for the same trip is ten dollars.  Several fools—­no, I mean several tourists—­usually go together, and divide up the expense, and thus make it light; for if only one f—­tourist, I mean—­went, he would have to have several guides and porters, and that would make the matter costly.