COMPLETE TITLE: Critical Reflections on Poetry, Painting and Music. With An Inquiry into the Rise and Progress of the Theatrical Entertainments of the Ancients. Written in French by the Abbé Du Bos, Member and perpetual Secretary of the French Academy. Translated into English by Thomas Nugent, Gent. From the fifth Edition revised, corrected, and inlarged by the Author. 
The title of the second volume says: Critical Reflections on Poetry and Painting. 
Online text: INTERNET ARCHIVE: Vol. I - Vol. II - Vol. III

Translation of Réflexions critiques sur la poésie et sur la peinture by Jean-Baptiste Dubos (see). 

RECENT EDITIONS: 
Reprint: New York, AMS Press, [1978].