In the book version of:
The Picture Of Dorian Gray, Ch. 3
Ward, Lock & Co., 1891
In the story the comment is made in general conversation by Erskine at a lunch given by Lady Agatha.
Perhaps, after all, America never has been discovered,' said Mr Erskine. 'I myself would say that it had merely been detected'.
In the earlier magazine version in:
Lippincott's Monthly Magazine Vol. XLVI, No. 271, July [June 20] 1890, pp. 3-100.
The quotation does not appear here as originally published in thirteen chapters.
In a Wilde manuscript list of aphorisms, c. 1890:
"It is a vulgar error to suppose that America was ever discovered. It was merely detected."
Manuscript: Clark Library MS W6721M3 P576
Book: Mason, 328.
Magazine: Mason, 81.
Bibliography of Oscar Wilde
by Stuart Mason, 1914
LONDON | T. WERNER LAURIE LTD.
Credit for the manuscript source:
The Complete Works of Oscar Wilde: The Picture of Dorian Gray : the 1890 and 1891 texts, Oxford University Press, 2005
Russell Jackson, Joseph Bristow, Ian Small