Capitalization in Austen's two Inches wide quote

What should I do with your strong, manly, spirited Sketches, full of Variety and Glow? -- How could I join them on to the little bit (two Inches wide) of Ivory on which I work with so fine a Brush, as produces little effect after much labour?

I love the above quote from Jane Austen. What are the canonical explanations for her capitalization of Sketches, Variety, Glow, Inches, Ivory, and Brush?

P.S. Apologies in advance if this question is outside of this forum's scope.

Solution 1:

Two good sources about capitalization in English literature:

"1) Q: In rereading Emily Dickinson’s poems, I’m impressed by her use of midline capitals. Can you shed some light on the capitalization of common nouns in 19th-century America? Is it intended for emphasis?

A: When William Caxton introduced printing to England in the 15th century, 'great uncertainty' surrounded the use of capital letters, according to the linguist David Crystal." Please read on.

capitalization

And this: Conditions of Literary Production from the Norton Anthology of English Literature, "The Restoration and the Eighteenth Century", 1660 to 1785

"Reading material, though it remained unaffordable to the laboring classes, was frequently shared. Circulating libraries began in the 1740s.

Capital letters began to be used only at the beginnings of sentences and for proper names, and the use of italics was reduced."

The Restoration and capital letters