Meanwhile the public and the critic ought to become familiar with the aspects of nature, in order to recognise the difference between the true poetry of painting, and the mere empty sentimentalism which was only the rant and bombast of landscape art.
With such feelings as these he wrote the third and fourth volumes of "Modern Painters," (published respectively January 15 and April 14, 1856).

The work was afterwards interrupted only by a recurrence of his old cough, in the exceptionally cold summer of 1855.

He went down to Tunbridge Wells, where his cousin, William Richardson of Perth, was practising as a doctor; it was not long before the cough gave way to treatment, and he was as busy as ever.

About October of that year he wrote to Mrs.Carlyle as follows, in a letter printed by Professor C.E.
Norton, conveniently summing up his year: "Not that I have not been busy--and very busy, too.

I have written, since May, good six hundred pages, had them rewritten, cut up, corrected, and got fairly ready for press--and am going to press with the first of them on Gunpowder Plot day, with a great hope of disturbing the Public Peace in various directions.