"Forty or fifty!" exclaimed Barbican. "They measured no fewer than a thousand and ninety-five lunar mountains and crater summits with a perfect success. Six of these reach an altitude of upwards of 18,000 feet, and twenty-two are more than 15,000 feet high." "Which is the highest in the lot?" asked Ardan, keenly relishing Barbican's earnestness. "_Doerfel_ in the southern hemisphere, the peak of which I have just pointed out, is the highest of the lunar mountains so far measured," replied Barbican. "It is nearly 25,000 feet high." "Indeed! Five thousand feet lower than Mount Everest--still for a lunar mountain, it is quite a respectable altitude." "Respectable! Why it's an enormous altitude, my dear friend, if you compare it with the Moon's diameter. The Earth's diameter being more than 3-1/2 times greater than the Moon's, if the Earth's mountains bore the same ratio to those of the Moon, Everest should be more than sixteen miles high, whereas it is not quite six." "How do the general heights of the Himalayahs compare with those of the highest lunar mountains?" asked Ardan, wondering what would be his next question. "Fifteen peaks in the eastern or higher division of the Himalayahs, are higher than the loftiest lunar peaks," replied Barbican. "Even in the western, or lower section of the Himalayahs, some of the peaks exceed _Doerfel_." "Which are the chief lunar mountains that exceed Mont Blanc in altitude?" asked Ardan, bravely suppressing a yawn. "The following dozen, ranged, if my memory does not fail me, in the exact order of their respective heights;" replied Barbican, never wearied in answering such questions: "_Newton_, _Curtius_, _Casatus_, _Rheita_, _Short_, _Huyghens_, _Biancanus_, _Tycho_, _Kircher_, _Clavius_, _Endymion_, and _Catharina_." "Now those not quite up to Mont Blanc?" asked Ardan, hardly knowing what to say. "Here they are, about half a dozen of them: _Moretus_, _Theophilus_, _Harpalus_, _Eratosthenes_, _Werner_, and _Piccolomini_," answered Barbican as ready as a schoolboy reciting his lesson, and pointing them out on the map as quickly as a compositor distributing his type. "The next in rank?" asked Ardan, astounded at his friend's wonderful memory. "The next in rank," replied Barbican promptly, "are those about the size of the Matterhorn, that is to say about 2-3/4 miles in height. They are _Macrobius_, _Delambre_, and _Conon_. Come," he added, seeing Ardan hesitating and at a loss what other question to ask, "don't you want to know what lunar mountains are about the same height as the Peak of Teneriffe? or as AEtna? or as Mount Washington? You need not be afraid of puzzling me. I studied up the subject thoroughly, and therefore know all about it."