Source, in full
Petra: A Poem, 2nd ed. (Oxford: F. Macpherson, 1846), pp. 23–4. Variants printed in Gems of English Poetry (London: T. Nelson, 1865), p. 287: 'It seems' for 'They seem'; 'erst' for 'once'; 'and consecrates' for 'or sanctifies'. Last line parodied by William Plomer, "A rose-red sissy half as old as time."