Answer:
From the opening sentence, we understand that there are thirteen bubbles that floated in the milk.
The author described the bubbles as "transparent hemispheres gleamed like souvenirs of the summer days just past, rich with blue reflections of the sky and of shadowy greens".
The effect of the author's choice of words was that of imagery as it helped the readers to "see" the bubbles in their mind's eye with such clarity as it was so succinctly described.
The author further described John's actions as he used the spoon to scoop the milk and swallow it in such a way that suggested he was either very hungry or in a hurry.
"John Hawkins jabbed the bubble closest to him with his spoon,. . .there was no mark of where it had been"
This description had the effect of making the readers know how eager John was to consume the milk and how quickly the ripples vanished.
The readers can also infer that John consumed the milk in an aggressive manner because of the way he jabbed at the ripple closest to him in his effort to drink the milk.
From the excerpt you posted it looks like the writer's primary purpose is to persuade the audience to share his point of view.
This can be seen in phrases like "it seems to me that the decision is easy", where he implies that he has enough knowledge to see something that the Township officials are not seeing.
B. Compound predicate nominative, A. Simple subject, D. gerund phrase
