Analysis of Sonnet XXIV: 'Farewell once more,--and yet again farewell!'

Farewell once more,--and yet again farewell!
I cannot quit thee. On thy lips I press
A parting kiss. I cease from my caress;
Slowly I loose thy waist; the troubled swell
Of thy fair bosom, with the sighs that tell
Thy own emotion, falls from me. I bless
Thy downcast head; upon each lustrous tress
Rest my poor hands, as if some sacred spell
Were in my benediction. Then I try
A sudden parting. Ah! how whirls my brain!
How pang crowds pang; how pain leaps over pain!
My purpose falters; o'er my senses fly
Oblivious clouds; and then--I know not why--
Lo! I am hanging on thy lips again!