In "A Modest Proposal," where does Swift use the rhetorical device of irony?

"A Modest Proposal" is one of Jonathan Swift's most brilliant satirical works, and the essay deftly uses irony in hilarious (and shocking) ways. As a reminder, irony is a reversal of our expectations, and it often involves the occurrence of something that was not expected. Swift uses irony brilliantly in the ninth paragraph of "Proposal," as found in the eText on : 

I have been assured by a very knowing American of my acquaintance in London, that a young healthy child well nursed, is, at a year old, a most delicious nourishing and wholesome food, whether stewed, roasted, baked, or boiled; and I make no doubt that it will equally serve in a fricasie, or a ragoust.

This statement comes out of nowhere and is completely unexpected. Prior to this statement, Swift began his essay by soberly discussing the many problems faced by Ireland, especially the impoverished status of much of the island's population. The tone is academic and intelligent, and so we get the sense that the solution that Swift will offer will be logical, well-informed, and completely reasonable. What we get instead is an increasingly insane discourse on the benefits of eating children and the suggestion that doing so will provide an enhanced food supply and economic relief (as there will be fewer mouths to feed). This turn of events is ironic because it runs completely contrary to our expectations. The above paragraph provides one of the essay's best examples of irony. It's one of the earliest moments that Swift proposes to eat Ireland's children, and so it is his most surprising use of irony.