Purl, Flip and Dog's Nose

Over twenty years on, I am re-reading Our Mutual Friend which I am enjoying all the more because I've forgotten most of the plot. One early scene is in a London pub where they serve Purl, Flip and Dog's Nose. The reference at the back describes these drinks. Purl and Flip are mulled ales, the first flavoured with gin, sugar and ginger and the second with sugar, spice, spirits and a beaten egg. Dog's Nose is beer and gin, the thought of which rather makes my stomach turn as I am not a great fan of either.
I was amused by the illiterate dustman, Mr Boffin, engaging Silas Wegg to read to him and Mrs Boffin. He suggests Wegg begins with "The Decline and Fall of the Rooshan Empire." Wegg arrives on his first day and is somewhat bemused when he picks up the book:
"This, Mr Boffin and Lady, is the first chapter of the Decline and Fall off____....Why it comes to my mind that you made a little mistake...I think you said Rooshan Empire, sir?"
"It is Rooshan, isn't it, Wegg?"
"No sir. Roman. Roman."
"What's the difference, Wegg?"
..."The difference, sir? There you place me in a difficulty, Mr Boffin. Suffice it to observe that the difference may best be postponed to some other occasion when Mrs Boffin does not honour us with her company."...
Then Mr Wegg in a dry unflinching way, entered on his task...stumbling at Polybius (pronounced Polly Beeious, and supposed by Mr Boffin to be a Roman virgin, and by Mrs Boffin to be responsible for the necessity of dropping it.)