Interested in Language
While reading a world-famous masterpiece of English literature written by J.R.R Tolkien, I have come across a good many usages which are difficult to find in standard ESL learning materials. And one of them - not the most difficult one, I suppose, but still requiring some clarifications - has been mentioned above in the topic. In order to give the context, I would like to cite a sentence from "The Hobbit":
"If he plunged into it, a vapour and a steam would arise enough to cover all the land with a mist for days; but the lake was mightier than he, it would quench him before he could pass through."
So, I am wondering why "a vapour", "a steam", and "a mist" were used as countable nouns, especially "a steam". I have also tried to guess at the reasons myself, and I suppose that the point is that in each case it may mean, so to say, a limited amount of the substance (just enough "to cover all the land") within certain limits in space - simply "a cloud of...". I am not 100% sure if I have got it right, so I need your help.
Thanks very much in advance.