Pietro approaches his father, Bernardo, with perhaps more deference than a twenty-first century twenty-five year-old might address their pater familias (a shame, perhaps my own Dad might say!), but an exchange early on in the dialogue is all too familiar. Bernardo exclaims that he is glad to have Pietro back from Sicily, and his son agrees, but gently emphasises that he had a wonderful time during his two years away. Bernardo responds as many a parent of a young person might today - with the observation that "I thought as much when up to now you hadn't spared a thought for us."
Shortly after, at Bernardo's urging, Pietro begins to tell the story of his trip - whilst away studying in Sicily - to visit Etna. He starts by saying that the trip took place after he and his companion, Angelo, had spent fourteen months without a break studying Greek literature. Though the stereotypes of Western modernity would be astonished at such dedication among their youth (mark that I say stereotypes!), modern parents would probably provide a similar, fussy chastisement as Bernardo does at this interlude: "No wonder you looked different and lost your colour! We thought you had grown thin and pale..."
As familial conversations often will, the dialogue meanders for a brief while before returning to the slopes of Etna, including a long musing from Bernardo that in spite of all the benefits he provided his son in his upbringing - a good education, a moral code - Pietro will ultimately "blame" him once he is gone for not leaving him with wealth. Pietro protests, prompting an interchange in which you can almost hear his growing exasperation in the face of his father's placid responses:
Pietro: ...do you really suppose I would be angry with you for not leaving me a country house and a wood of plane trees? You must not think that, father.
In his turn, Pietro responds like any young person delighted with their own adventures, saying that instead they waited for the stones to cool and picked them up as souvenirs, "led on by our eagerness - or perhaps our greed - to see everything". Bernardo attempts to get through to his son once more, pointing out that this sort of "thorough" interest was exactly what led Pliny the Elder (a Roman naturalist who died during the AD 79 eruption of Vesuvius) to an over-warm end. Pietro says he knew this, but that he and his companions "were so delighted with the spectacle, and filled with such amazement at the novelty of the phenomenon, that none of us gave a thought to himself."
The conversation then shifts from what Pietro observed to what Bernardo can explain, with the benefit of a classical education: precisely how the fires of Etna came to be and how and why they continue to burn. The passage is a dialogue, not a transcript, so it is probable (as suggested by Mary P. Chatfield, the modern translator of the Latin work) that Pietro is flatteringly putting into his father's mouth the explanations that he himself wants to give in a text written, as he explains at the very start, for the benefit of everyone who wanted to know about his Etna trip.
I believe this serves a further three purposes. Firstly, it enables Pietro to become the voice for the reader's own probing questions. Secondly, it provides a clear distinction between empirical, experiential knowledge (as expressed by Pietro in the dialogue), and scholarly, ancient, text-based knowledge (offered by Bernardo). However, in the interchange between the two - Bernardo keen to hear of Pietro's experience, Pietro eager to learn from his father - the dialogue also highlights that these two forms of knowledge complement and inform one another.
Beyond this explanatory passage, the dialogue comes to a rather abrupt, but recognisably filial end. Talk of a natural fountain on one side of Etna leads Pietro to begin speaking of local legends of Faunus, a horned god "wreathed in pine-branches, generally silent, but sometimes solacing his loves on a pipe." Recalling to whom he is speaking, however, Pietro stops himself, saying that when he speaks to his father, he "should be serious". He is not, however, entirely contrite, adding as he does that he thinks it is sometimes necessary for learned men to take a break from sombre matters and to speak of "those lighter subjects of legend".
This provides Bernardo with the opportunity in the dialogue - as well he may have in real life - to close the conversation with a fatherly moral to his son:
This is always my chief advice to you throughout your life, Pietro; for unless you train yourself to make your mind impervious to the allurements of pleasures, they will assail you in countless forms, entice and ensnare you, even defeat and overpower you, not only when you are young, as you are now, but also when you are a grown man.