Ruskin was first elected to the Slade Professorship of Fine Art in
Oxford in 1869, and held the chair continuously until 1878, when
he resigned because of ill-health, and again from 1883 to 1885.
The _Lectures on Art_ were announced in the _Oxford University
Gazette_ of January 28, 1870, the general subject of the course
being "The Limits and Elementary Practice of Art," with Leonardo's
_Trattato della Pittura_ as the text-book. The lectures were
delivered between February 8 and March 23, 1870. They appeared in
book form in July of the same year. These lectures contain much of
his best and most mature thought, of his most painstaking research
and keenest analysis. Talking with a friend in later years, he
said: "I have taken more pains with the Oxford Lectures than with
anything else I have ever done": and in the preface to the edition
of 1887 he began: "The following lectures were the most important
piece of my literary work, done with unabated power, best motive,
and happiest concurrence of circumstance." Ruskin took his
professorship very seriously. He spent almost infinite labour in
composing his more formal lectures, and during the eight years
in which he held the chair he published six volumes of them, not
to mention three Italian guide-books, which came under his
interpretation of his professional duties;--"the real duty
involved in my Oxford Professorship cannot be completely done by
giving lectures in Oxford only, but ... I ought also to give what
guidance I may to travellers in Italy." Not only by lecturing and
writing did he fill the chair, but he taught individuals, founded
and endowed a Drawing mastership, and presented elaborately
catalogued collections to illustrate his subject. His lecture
classes were always large, and his work had a marked influence in
the University.