letting her know he was there in a manner sufficiently potential
In this case, “potential” is used to mean “possessing potency or power;” this is closer to its etymological meaning than to the more common definition, “possible.” “Potential” comes from the Latin word potentia, meaning power. Archie must make himself known to Lady Ongar in a powerful way if she is to take notice of him. The use of the word here also plays on the more common meaning of “possible,” since at this point Archie’s fate as concerns Lady Ongar is not certain, but is still changeable. [SH 2012]
Harpies were winged female monsters in mythology, especially known for torturing Phineas by stealing his food daily. The word “harpy” comes from the Greek verb harpazo and literally means “snatcher.” Here, Archie Clavering compares lawyers to harpies because “there is no end to their charges,” implying that they essentially steal money from their clients. [SH 2012]
which do you like best, the town or the country?
To this question of Sophie Gourdeloup’s, Lady Ongar responds, “Whichever I’m not in, I think.” In one of Horace’s satires, a slave accuses his master of exactly this fickleness. Sophie suggests that Lady Ongar is restless because she is idle; Horace seems to suggest that this restlessness is partly due to having money and the ability to indulge one’s every whim. By bringing in this reference to Horace, Trollope shows that the fickleness and dissatisfaction of the rich are age-old problems.
Sources: Horace, Satire 2.7.28-29.
to be very fond of your friends…it is the salt of life
This is a paraphrase of the Latin proverb vitae sal amicitia, “friendship is the salt of life.” Sophie Gourdeloup speaks this line of worldly wisdom, which at first seems appropriate since her name comes from the Greek word for wisdom. However, Sophie does not seem to be a trustworthy character at this point in the novel; neither Lady Ongar nor Harry Clavering considers her a true friend. With these relationships at play, then, it seems odd for Sophie to deploy this proverb about friendship when she is speaking to those with whom she can claim only a pseudo-friendship. [SH 2012]