Non-rhotic pronunciation continued to influence American prestige speech until the 1860s, when the American Civil War began to shift America's centers of wealth and political power to rhotic areas with fewer cultural connections to the old colonial and British elites. The advent of radio and television in the 20th century established a national standard of American pronunciation that preserves historical , with rhotic speech in particular becoming prestigious in the United States rapidly after the Second World War. The earliest traces of a loss of in English appear in the early 15th century and occur before coronal consonants, especially , giving modern "ass (buttocks)" (Old English "ears", Middle English "ers" or "ars"), and "bass (fish)" (OE "bærs", ME "bars"). A second phase of -loss began during the 15th century, and was characterized by sporadic and lexically variable deletion, such as "monyng" "morning" and "cadenall" "cardinal". These -less spellings appear throughout the 16th and 17th centuries, but are uncommon and are restricted to private documents, especially ones written by women. No English authorities describe loss of in the standard language prior to the mid-18th century, and many do not fully accept it until the 1790s. During the mid-17th century, a number of sources describe as being weakened but still present. The English playwright Ben Jonson's "English Grammar", published posthumously in 1640, records that was "sounded firme in the beginning of words, and more liquid in the middle, and ends." The next major documentation of the pronunciation of appears a century later in 1740, when the British author of a primer for French students of English said: "...in many words "r" before a consonant is greatly softened, almost mute, and slightly lengthens the preceding vowel". By the 1770s, postvocalic -less pronunciation was becoming common around London even in more formal, educated speech. The English actor and linguist John Walker used the spelling "ar" to indicate the long vowel of "aunt" in his 1775 rhyming dictionary. In his influential "Critical Pronouncing Dictionary and Expositor of the English Language" (1791), Walker reported, with a strong tone of disapproval, that "... the "r" in "lard", "bard", [...] is pronounced so much in the throat as to be little more than the middle or Italian "a", lengthened into "baa", "baad"..."