I have this book..Pegasus Descending
....which has several of McGonagall's poems about the bridge. The first celebrates its construction. The second, "The Newport Railway" is about the rail line which crossed the bridge and made going from Newport to Dundee easier. Then came the famous 'disaster' poem. Finally, the is "An Address to the New Tay Bridge" with its "strong brick tiers and buttresses in so grand array".