The message translates as:
I have waited for you all day. I beg you - a woman on her knees beseeches you to help her in her desperation. I will spend the night praying for you to come. At dawn I will be in the little barn near to the sea reached by the first path on the left after the farm.
A Piccadilly collar is a stiff half-circular shirt collar made from plastic or celluloid. A Shakspere's collar is a soft, pointed collar. A dog collar is the kind of black and white band collar worn by priests. A Dux collar is a narrow, stiff high collar with the points turned down.
Newmarket is arguably the most famous horse racecourse in England.
"Imprimatur" is a Latin term now used to mean a seal of approval. "Ducatur in matrimonium" means being led into marriage.
A sovereign is a coin equal to £1, or 20 shillings. A valet similar to Sam would probably have earnt in the region of £20-30 a year (source). A bed in a shared room in the cheapest London lodgings would cost around £1 a year.
"In extremis" means, in Latin, "at the last point of death" or, more generally, in any extreme situation. "De profundis" means "from the depths", and is a line from Psalm 130, a song of penitence and near-despair. "De altis" means "from the heights".
Socrates (469-399 BCE), one of the greatest Classical philosophers, was sentenced to death by the city-state of Athens after being found guilty on a charge of corrupting the youth of the city. He was called a "gadfly" of the state because of his outspoken opposition to the social and political status quo and it is probably this commitment to speaking truth to power to which Grogan refers.
Attributed to Socrates among others, the dictum "know thyself" was written into the stones of the courtyard of the Delphic oracle.
When Malthus discusses the theory of human eugenics, he rejects the idea because it would require the consignment of all the "bad specimens" to celibacy.
Although the regime in asylums underwent a great deal of improvement in the first half of the 19th century, the treatment of inmates was still far below modern standards and asylums were still disturbing places. This is taken from a description of female asylum inmates in 1858:
"It was clear that they retained the instincts of their sex without its clearness. Yet there were some to whom the novelty of a stranger offered no excitement - who sat huddled up by the window, with scowling eyes and dishevelled hair, flesh-and-blood pictures of despair." (source)