The Hearth and the Salamander - An Explanation

I tried to look up the meaning of the chapter, and wanted to see how that fits the title of the book. They define hearth as paved surface in front of the fireplace, whereas as salamander is a kind of lizard. None of them make sense to what the storyline is, but if one looks harder they may find some connection to them both.
My explanation is that the hearth is where Guy hides all his books saved from being incinerated. This is the storing place; before they end up in the fire, it is very hot here. This is like how in front of the fireplace they have a bricked or stoned finish which will be hot and one does not place anything of importance that close. So maybe Guy was protecting all those books from fire, but in reality they are were all in danger of fire and will end burnt or damaged anyway. Guy tried but in the end, as Beatty said "fire is clean and powerful" and all the books vanished.
Whereas the Salamander is a metaphor for the mechanical hound. It is scary looking and an reptile. Some even define Salamander as an medieval creature, a character in role playing games. This fits the description very well for the hound, who eradicates those who oppose and are resistance elements.