Now that's enough, said the Astronomer with a kind of gentleness that was obviously manufactured for the benefit of strangers and which had beneath it an easily-recognized edge.
He did not want them to embarrass themselves in front of the strangers. 
mnli hypothesis: He did not want them to embarrass themselves in front of the strangers.  premise: Now that's enough, said the Astronomer with a kind of gentleness that was obviously manufactured for the benefit of strangers and which had beneath it an easily-recognized edge.