All 3 Uses

felicity
in
Moby Dick
(Auto-generated)

For now, since by many prolonged, repeated experiences, I have perceived that in all cases man must eventually lower, or at least shift, his conceit of attainable felicity; not placing it anywhere in the intellect or the fancy; but in the wife, the heart, the bed, the table, the saddle, the fireside, the country; now that I have perceived all this, I am ready to squeeze case eternally.
Chpt 94-96 *

felicity = happiness
For, thought Ahab, while even the highest earthly felicities ever have a certain unsignifying pettiness lurking in them, but, at bottom, all heartwoes, a mystic significance, and, in some men, an archangelic grandeur; so do their diligent tracings-out not belie the obvious deduction.†
Chpt 106-108

Uses with a meaning too rare to warrant foucs:

Nor, at the time, had it failed to enter his monomaniac mind, that all the anguish of that then present suffering was but the direct issue of a former woe; and he too plainly seemed to see, that as the most poisonous reptile of the marsh perpetuates his kind as inevitably as the sweetest songster of the grove; so, equally with every felicity, all miserable events do naturally beget their like.†
Chpt 106-108 *

Definitions:

(1) (felicity as in: domestic felicity)
happiness or luck; or an instance or source of such
(2) (felicity as in: felicity of expression)
pleasing and appropriate manner or style; or an instance of such
(3) (meaning too rare to warrant focus)
Less commonly, Felicity is the first name of a female.