Page 234. " Nine men out of ten would flee from a Royal Society soiree in the extremity of boredom; but Creighton was the tenth "
Royal Society, London
GNU Free Documentation LicenseRoyal Society, London - Credit: Kaihsu Tai

The Royal Society of London for the Improvement of Natural Knowledge, known simply as the Royal Society, is dedicated to the furthering of the sciences and is arguably the oldest such society in existence. 

In Kim, this great national treasure becomes a symbol for the nostalgia of the British Empire's elite. Mired in the intrigue of the Great Game, Creighton yearns for the ‘crowded rooms in easy London’ full of ‘bald-headed gentleman who know nothing of the army’.

Page 245. " “There is no caste when men go to – look for tarkeean.” "
Creative Commons Attributionkedgeree - Credit: Kirsten Loza, Flickr

Tarkeean, as Kim points out, is another name for kedgeree, a simple rice-based curry that even the poorest man in India could afford. Hence 'there is no caste' has a double meaning, referring both to the curry dish as available to any hungry man, and to the Great Game as open to all, regardless of caste, race or creed.