Arthur Griffiths, Mysteries of Police and Crime, Vol…
“ So much for the police in uniform. That in plain clothes, en bourgeois, as the French call it, is not so numerous, but it fulfils a higher, or at least a more confidential, mission. Its members are styled inspectors, not agents, and their functions fall under four principal heads. There is, first of all, the service of the Sûreté—in other words, of public safety—the detective department, employed entirely in the pursuit and capture of criminals, of which more anon ”
