This is a difficult topic and requires a lot of research or discussing with an expert.
I would advise finding some English texts from the 1850s and comparing them to modern texts.
You can use this Webster's 1828 dictionary
http://www.wealth4freedom.com/wns/Webster.htmand compare with modern definitions at
http://www.websters.comhttp://www.answers.com/topic/english-languageHere is some suggested reading:
See H. L. Mencken, The American Language (rev. 4th ed. 1963); G. W. Turner, The English Language in Australia and New Zealand (1966);M. Pei, The Story of the English Language (new ed. 1968); P. Roberts, Modern Grammar (1968); M. M. Orkin, Speaking Canadian English (1971); T. Pyles and J. Algeo, The Origins and Development of the English Language (3d ed. 1982); W. F. Bolton, A Living Language (1982); B. Kachru, ed., The Other Tongue (1982); R. Hudson, Invitation to Linguistics (1984); J. Baugh, Black Street Speech (1985); The Random House Dictionary of the English Language (2d ed. 1987).