Nailing it on the head, sent an email to Professor Hooker this morning, this is what I got back.....
Excellent moss (and tiompan for first mentioning it)! Good to get that sorted, and I'll make the necessary corrections over the weekend. "The quotation you ask about is from John Ormond's poem 'Ancient Monuments'. I don't have the Ormond poem with me, but my recollection is that it is dedicated to Alexander Thom. That would account for it being ascribed to Thom on a megalithic forum. It is also just possible that Ormond quotes a phrase or a few words from Thom in the poem. But the verses are certainly from Ormond's poem."