Sentence:  ... on so small a scale, it would be impossible to give an adequate idea of a grand scene. ... Were it painted indeed with exactness on a pane of glass in a window, and the eye brought to it, under the deception of it's being a real view; the imagination might <WSD>aggrandize</WSD> it. 
Meaning of the word marked with <WSD> tags:  To make great; to enlarge; to increase.