Sentence:  In "Heroic Verse", but especially in the "grander Lyrics", there are sometimes such noble Elevations of Thought and Passion as illuminate all Things around us, and convey to the Soul most exalted and magnificent Images and sublime Sentiments: These furnish us with glorious Springs and "Mediums" to raise and <WSD>aggrandize</WSD> our Conceptions ... 
Meaning of the word marked with <WSD> tags:  To make great; to enlarge; to increase.