By water, wood and hill...

[TThurston]

I wonder about the list of things in the rhyme Tom teaches the hobbits:

Ho! Tom Bombadil, Tom Bombadillo!
By water, wood and hill, by the reed and willow,
By fire, sun and moon, harken now and hear us!
Come, Tom Bombadil, for our need is near us.

We discussed this at some length, but did not really address what the word "by" means. I wonder if it indicates the means by which Tom would be informed of their call for help. For example, hear us when the water tells you, or when the wood tells you, or the hill. When Frodo does invoke the rhyme, it says that the dark chamber echoed as if to the sound of drum and trumpet. Tom's response came "as it was coming down though the ground or thick walls." It almost sounds as though the ground of the hills is the medium by which Frodo has called Tom and by which he hears his response.

 

[Matt DeForrest]

A good reading, TThurston. The three options for by here appear to be through (as you have argued), place (the places he could be when he harkens, which I tend to lean to) or as powers used to compel. Given that Bombadil is Master, the latter seems unlikely, even if it is only to compel him to hear and not to act.

In truth, I had not considered your option but since someone or something told him about the four hobbits being abroad, I suspect you are on to something here.

 

[amysrevenge]

It seems like this use of "by" is related to Frodo's distinction of Gollum swearing his oath "on" the Ring compared to "by" it. Invoking a thing without requiring its presence at the time.