Definition of "treatise"

"As you cannot make a speech, you must," said Henrietta, "put it into a treatise."

1837, L[etitia] E[lizabeth] L[andon], “An Act of Parliament”, in Ethel Churchill: Or, The Two Brides. […], volume II, London: Henry Colburn, […], page 191

“ […] We are engaged in a great work, a treatise on our river fortifications, perhaps ? But since when did army officers afford the luxury of amanuenses in this simple republic ? […]”

1910, Emerson Hough, chapter I, in The Purchase Price: Or The Cause of Compromise, Indianapolis, Ind.: The Bobbs-Merrill Company

And if someone wants to know how to make objections to actual craftsmen themselves on the subject of art in general or any particular art, there are published treatises available, as you know.

2005, Plato, translated by Lesley Brown, Sophist, page 232d

Some poems, echoing the purpose of early poetic treatises on scientific principles, attempt to elucidate the mathematical concepts that underlie prime numbers. Others play with primes’ cultural associations. Still others derive their structure from mathematical patterns involving primes.

2013 July-August, Sarah Glaz, “Ode to Prime Numbers”, in American Scientist, volume 101, number 4