[Footnote: _With laugh repress'd_, l. 434. The cause of the violent actions of laughter, and of the difficulty of restraining them, is a curious subject of inquiry. When pain afflicts us, which we cannot avoid, we learn to relieve it by great voluntary exertions, as in grinning, holding the breath, or screaming; now the pleasurable sensation, which excites laughter, arises for a time so high as to change its name, and become a painful one; and we excite the convulsive motions of the respiratory muscles to relieve this pain. We are however unwilling to lose the pleasure, and presently put a stop to this exertion; and immediately the pleasure recurs, and again as instantly rises into pain. Which is further explained in Zoonomia, Sect. 34. 1. 4. When this pleasurable sensation rises into a painful one, and the customs of society will not permit us to laugh aloud, some other violent voluntary exertion is used instead of it to alleviate the pain.] [Footnote: _With smile chastised_, l. 434. The origin of the smile has generally been ascribed to inexplicable instinct, but may be deduced from our early associations of actions and ideas. In the act of sucking, the lips of the infant are closed round the nipple of its mother, till it has filled its stomach, and the pleasure of digesting this grateful food succeeds; then the sphincter of the mouth, fatigued by the continued action of sucking, is relaxed; and the antagonist muscles of the face gently acting, produce the smile of pleasure, which is thus during our lives associated with gentle pleasure, which is further explained in Zoonomia, Sect. 16. 8. 4.] Now at her nod the Nymphs attendant bring Translucent water from the bubbling spring; In crystal cups the waves salubrious shine, Unstain'd untainted with immodest wine. Next, where emerging from its ancient roots Its widening boughs the Tree of Knowledge shoots; 440 Pluck'd with nice choice before the Muse they placed The now no longer interdicted taste. Awhile they sit, from higher cares released, And pleased partake the intellectual feast. Of good and ill they spoke, effect and cause, Celestial agencies, and Nature's laws.