"Happy" here feels loaded--for obvious reasons when thinking about the comparison between enslaved laborers and Scottish miners. But it's also loaded in relation to the georgic tradition: one of Virgil's most optimistic moments, in a poem that vacillates pointedly between optimism and pessimism, is his "happy husbandman." In Dryden's translation: "Oh happy, if he knew his happy State! / The Swain, who, free from Business and Debate; / Receives his easy Food from Nature's Hand, / And just Returns of cultivated Land!"

The Muse has seen, not the poet.