The fact that Swift uses such a scholarly, formal tone in this excerpt only makes it more clear that he is using verbal irony. Irony refers to the use of devices and circumstances that represent the opposite of what is to be expected. In this case, the subject is extremely horrible (the killing and breeding of children), but the tone is not as desperate and angry as would be expected. Instead, it is calm, collected and scholarly. This is an example of verbal irony.
