In 1871 the Ørsted scale was extended with plus and minus-steps, and numeral values were added accordingly.
ɪn wˈʌn θˈaʊzənd ˈeɪthˈʌndɹɪd sˈɛvənti wˈʌn ðɪ ˈɔːɹstᵻd skˈeɪl wʌz ɛkstˈɛndᵻd wɪð plˈʌs ænd mˈaɪnəsstˈɛps, ænd nˈuːmɚɹəl vˈæljuːz wɜːɹ ˈædᵻd ɐkˈoːɹdɪŋli.