post and its combox, I deduce that Poul Anderson's works contain:
two appearances by Holmes and Watson;
two descendants of Holmesian characters, Holmes himself and Moriarty;
two extraterrestrial counterparts of Holmes, a Martian and a Hoka.
This is the kind of symmetry that I notice and that the author was unaware of.
To move forward, I am reading more widely and as always reflecting on Poul Anderson's place in the scheme of things. It is usually possible to find a connection with his works. I have stumbled on the major theme of cosmic crises which might require more than one post. My treatment of it will be "divided into three parts" (see here):
(i) works by other authors;
(ii) works by Anderson;
(iii) an explanation of how this theme arose.
(i) The cosmos is routinely threatened in comic books (see here) but what happens in prose fantasy and sf?
James Blish's Black Easter ends with Armageddon but this seems to be a merely Terrestrial affair. In the sequel, the fortress of Dis manifests in Death Valley and Satan, now God, consults the human magicians who had intitiated Armageddon. Blish's Cities in Flight ends with a collision between the matter and anti-matter universes: definitely (multi-)cosmic.
(ii) Poul Anderson's Tau Zero encompasses cosmic collapse but only because, thanks to time dilation, the characters live that long. The collapse does not happen in their normal lifetimes. A threat to the cosmos is envisaged in Starfarers (see here).
To Be Continued.