"You see," Captain Morhange said to me a week later, "that I was right
in advising you to go farther south before making for Shikh-Salah.
Something told me that this highland of Egere was not interesting from
your point of view. While here you have only to stoop to pick up
pebbles which will allow you to establish the volcanic origin of this
region much more certainly than Bou-Derba, des Cloizeaux, and Doctor
Marrés have done."

This was while we were following the western pass of the Tidifest
Mountains, about the 25th degree of northern latitude.

"I should indeed be ungrateful not to thank you," I said.

I shall always remember that instant. We had left our camels and were
collecting fragments of the most characteristic rocks. Morhange
employed himself with a discernment which spoke worlds for his
knowledge of geology, a science he had often professed complete
ignorance of.

Then I asked him the following question:

"May I prove my gratitude by making you a confession?"

He raised his head and looked at me.

"Well then, I don't see the practical value of this trip you have
undertaken."

He smiled.