To reassure @agent_smith - from my understanding of copyright liability, having a link to the book hosted on another site is unlikely to result in any risk to IGKT.
Great book and thanks for highlighting it here @Dan_Lehman!
Whoever is behind the https://www.conovers.org/ site is carrying the (small) copyright infringement risk. However since the book is very niche, currently unavailable in print form, the sharing is being done without any profit motive, and the copyright is held by the National Speleological Society (copyright notice is undated, but the book looks to have been published ~1971) which I imagine is a non-profit organisation, I think it's unlikely they'll hit conovers.org with a DMCA takedown.
This version being publicly available increases the chances that this knowledge remains useful to humanity. I'm all for this kind of preservation.
PS. The conovers.org site is a gloriously old-school reminder of what the early web was like! The guy is clearly a polymath genius.