The phrase "art by which" is correct and usable in written English.
It can be used to describe a specific type of art or method that serves a particular purpose or function.
Example: "The exhibition showcased various forms of art by which emotions are expressed through color and form."
Alternatives: "art that" or "art through which".
The beautiful ladder must therefore be his art, by which he will ascend, per ardua ad astra.
It is her art, by which we may be purified and saved; by which we may be engulfed and even destroyed.
With scholarly assurance and meticulous care, he builds the case that "theater is the art by which human beings make human action worth watching".
The great film critic Manny Farber once praised what he called "termite art," by which he meant the kind of small, stubborn movie that chews its way through a narrow piece of turf.
With the epistle he reached the summit of the highly subtle art by which he defined himself, a poet of the court and also a Protestant, aspiring to a pure and simple happiness of true religious faith.
They are the Cubists of contemporary art – by which I mean profound pioneers who opened the way for everything since – and yet whose originality has never quite been equalled.
For he did not practise oratory with a view to pleading causes, nor would he stoop to salute, embrace, and entertain the vulgar, which were the usual insinuating arts by which many grew popular.
This rapid expansion of chemical knowledge soon necessitated classification, for on the classification of chemical knowledge are based not only the systematized literature of chemistry but also the laboratory arts by which chemistry is passed on as a living science from one generation of chemists to another.
For this reason, it is believed that the original name had an initial h-sound, a fact that has led Serbian scholar Ljubinko Radenković to reject the etymology given by several dictionaries, including that of the Serbian Academy of Sciences and Arts, by which the demon's name comes from the Turkish word 'ala' (snake) as that word lacks the h-sound.
It matters because our movies are our leading story-telling medium - the predominant art form by which we express our collective dreams.
"The art world, by which I mean critics, dealers, everyone except the artist, is interested in the new and forgets everything else," Jack Tworkov noted not long before he died.
