On the dull, scaly, slate-colored skin somewhere above the shoulder, there was a singular black circle of some substance which looked like asphalt.  None of us could suggest what it meant, though Summerlee was of opinion that he had seen something similar upon one of the young ones two days before.  Challenger said nothing, but looked pompous and puffy, as if he could if he would, so that finally Lord John asked his opinion direct.

“If your lordship will graciously permit me to open my mouth, I shall be happy to express my sentiments,” said he, with elaborate sarcasm.  “I am not in the habit of being taken to task in the fashion which seems to be customary with your lordship.  I was not aware that it was necessary to ask your permission before smiling at a harmless pleasantry.”

It was not until he had received his apology that our touchy friend would suffer himself to be appeased.  When at last his ruffled feelings were at ease, he addressed us at some length from his seat upon a fallen tree, speaking, as his habit was, as if he were imparting most precious information to a class of a thousand.

“With regard to the marking,” said he, “I am inclined to agree with my friend and colleague, Professor Summerlee, that the stains are from asphalt.  As this plateau is, in its very nature, highly volcanic, and as asphalt is a substance which one associates with Plutonic forces, I cannot doubt that it exists in the free liquid state, and that the creatures may have come in contact with it.  A much more important problem is the question as to the existence of the carnivorous monster which has left its traces in this glade.  We know roughly that this plateau is not larger than an average English county.  Within this confined space a certain number of creatures, mostly types which have passed away in the world below, have lived together for innumerable years.  Now, it is very clear to me that in so long a period one would have expected that the carnivorous creatures, multiplying unchecked, would have exhausted their food supply and have been compelled to either modify their flesh-eating habits or die of hunger.  This we see has not been so.  We can only imagine, therefore, that the balance of Nature is preserved by some check which limits the numbers of these ferocious creatures.  One of the many interesting problems, therefore, which await our solution is to discover what that check may be and how it operates.  I venture to trust that we may have some future opportunity for the closer study of the carnivorous dinosaurs.”

“And I venture to trust we may not,” I observed.

The Professor only raised his great eyebrows, as the schoolmaster meets the irrelevant observation of the naughty boy.

“Perhaps Professor Summerlee may have an observation to make,” he said, and the two savants ascended together into some rarefied scientific atmosphere, where the possibilities of a modification of the birth-rate were weighed against the decline of the food supply as a check in the struggle for existence.