PUBLISHED IN: The Harleian Miscellany: or, A Collection of Scarce, Curious, and Entertaining Pamphlets and Tracts, As Well as Manuscript as in Print, Found in the late Earl of Oxford's Library. Interspersed with Historical, Political, and Critical Notes, London, Thomas Osborne, 1744, vol. V.

LATER EDITIONS:
An Essay on the Theatres: or, The Art of Acting; a Poem. In imitation of Horace's Art of Poetry, London printed, and Dublin re-printed by and for J. Kinneir, and A. Long, 1745, in-12, 24 pp. 

The text was published in the later editions of The Harleian Miscellany (London, Robert Dutton, 1811, vol. XII, pp. 146-157).

Online text: INTERNET ARCHIVE