Definition of "tristeness"

I think I have somewhere met with the observation that nobody ever leaves paris but with a degree of tristeness.

1785 June 6, Abigail Adams, edited by Julian P. Boyd, Mina R. Bryan, and Elizabeth L. Hutter, The Papers of Thomas Jefferson, volume 8 (25 February to 31 October 1785), Princeton, N.J.: Princeton University Press, published 1990, page 178

This gloomy tristeness reigns triumphant over most of the streets, except when a review, or some other public occasion, attracts the population of the provinces. […]; and, owing to there being no theatres, concerts, balls, or merry-making, an air of indescribable tristeness pervaded every thing, rendered still more melancholy by the number of people attired in that mournful garb which told of the loss of some beloved relative, or valued friend. […] Solitude had usurped the throne of gaiety; gloom and tristeness were the substitutes for mirth and music: […]

1836, Sketches of Germany and the Germans, with a Glance at Poland, Hungary, & Switzerland, in 1834, 1835, and 1836, volume I, London: Whittaker & Co., pages 67, 127, and 282

Opposite Simone the cat and the sportive Georgette were having a low-voiced conversation about the tristeness of a monsieur of their acquaintance.

1927, Jean Rhys, “Mannequin”, in Ann Reit, editor, The World Outside: Collected Short Fiction About Women at Work, New York, N.Y.: Four Winds Press, published 1977, page 138