Proclamations stated (the Latin "clamare" means "to cry out") new laws or rules that had to be followed. Although only thirteen, the narrator Isabel is unlikely to live long enough to benefit from America's "Emancipation Proclamation" (issued in 1863 during the Civil War).
I took a slow turn around the shop, admiring the shelves heavy with books, business forms, proclamations from Parliament and General Howe, slates, thick paper, quills, and sealing wax.
"Treatise" and "tract" are synonymous nouns, but a tract is often shorter, because a treatise would have more exposition ("a systematic interpretation or explanation of a topic"). The list of titles seems almost humorous, because one concerns sheep sex ("propagation" means "the act of producing offspring") while another is concerned about growing old; the most interesting book to Isabel would be the poems of Phillis Wheatley (an educated slave who was emancipated after her master's death).
The titles were near as long as books themselves: Treatise on the Propagation of Sheep, the Manufacture of Wool, and the Cultivation and Manufacture of Flax, by John Wily, or Cato Major, Or His Discourse of Old-Age: With Explanatory Notes, by M. T. Cicero, or Poems on Various Subjects, Religious and Moral, by Phillis Wheatley, and countless tracts containing sermons and advice.
I was the dogsbody in charge of keeping the oven stoked with wood and the ashes cleared out, fetching forgotten ingredients from the market, and beating eggs, ten at a time, till my arm was near to fall off.
Compare with "brook" (Chapter 1-11) and "abide" (Chapters 23-33): although the definitions are identical, the Latin "durare" means "to harden" and makes "endure" seem more like a test of strength, as suggested by this example sentence, than of attitude.
My back, my shoulders, my arms, they pulled with the strength of a thousand armloads of firewood split and carried, of water buckets toted for miles, of the burdens of every New York day and New York night boiled into two miles of water that I was going to cross.