Discovering Sherlock Holmes - A Community Reading Project From Stanford University

Waterloo Station, or the London & Southwestern Railway Terminus,
is at the top left of the map

Illustration from the American reprint

"…and the estates extended over the borders into Berkshire in the north, and Hampshire in the west."
That is, the estate was so large it extended into two neighboring counties.

"…in the days of the Regency."
Between 1811 and 1820, the future King George IV ruled as Regent for his father, George III, who suffered from periodic insanity.

"…and went out to Calcutta…."
The capital of Britain's Indian colony.

"Violence of temper approaching to mania has been hereditary in the men of the family, and in my stepfather's case it had, I believe, been intensified by his long residence in the tropics."
The self-justifying mythology surrounding British colonial rule of India centered on the terrible "trials" the British suffered for the sake of "civilizing" the Indian people. Chief among these "trials" was the tropical climate (with its attendant diseases, like malaria), which was considered to be bad for the British "constitution," and sometimes to be the cause of madness.

"He had no friends at all save the wandering gipsies, and he would give these vagabonds leave to encamp upon the few acres of bramble-covered land which represent the family estate, and would accept in return the hospitality of their tents, wandering away with them sometimes for weeks on end."
The "gipsies" (gypsies), or Roma, as they prefer to be called today, are a nomadic people from northern India who migrated west to Europe in the 14^th century. In Conan Doyle's time, their true origins were unknown, but there were many theories. Their dark skin, itinerant lives, and different customs made them convenient scapegoats for problems without an obvious cause: thefts, well-poisoning, livestock deaths, etc. The fact that Dr. Roylott lives with the gypsies would make him suspect in the eyes of many of Conan Doyle's readers.

"He has a passion also for Indian animals, which are sent over to him by a correspondent, and he has at this moment a cheetah and a baboon…."
While cheetahs do exist in India, baboons are found only in Africa.

"…who lives near Harrow…."
Harrow is a northwest borough of London, bordering on Hertfordshire.