Read it through once

‘Tis a life-long toil till our lump be leaven-- The better! What’s come to perfection perishes. Things learned on earth, we shall practise in heaven: Works done least rapidly, Art most cherishes. Thyself shalt afford the example, Giotto! Thy one work, not to decrease or diminish, Done at a stroke, was just (was it not?) “O!” Thy great Campanile is still to finish.