Few posts ago "Mark Hobson" at "The Landscapist" gave the cyclic set of explanations of his framing techniques. This time I followed the whole chain and and the most referenced photographer was: Peter Henry Emerson.
So I made some searches with google and came up with the very pleasant discovery of the photography section of the Internet Archive.
I am not a great fan of Microsoft but when it comes to culture I have to say that their fundings are well spent. Well done and a gratefull thanks.
There inside I have found the "Naturalistic photography for students of the art (1889)"
by Peter Henry Emerson himself.
I have read the intros from several other authors too. Along the intro you will always find a dissertation upon theory of photography a thing that is missing in a lot of modern photography handbooks. Such a dissertation, as a side effect, reveals from the beginning the position of the author/photographer. The newest handbooks I found with such dissertations where from Feininger 1960/70.
Since photography is such a practical art when the writer is a true photographer the theory rapidly becomes a personal statement about the artist's inner vision of his/her art.
That's the part that I value the most. While techniques come and go (and not always for the best) the essence, the photographer, remains.
Anyway reading online those books is a great Internet experience, you can also download them in various formats.