Analysis of To A Gentleman

I hope, Sir, by this you have found your Account,
In visiting Airy, and seeing his Mount:
If Froth can delight you, you're wonderous happy;
And we know it gives Joy on a Bottle of Nappy.
Your Friend would be very much mended, in troth,
Should Airy bestow him a Dash of his Froth:
To keep up the Metaphor, 'twould make him mellow,
And of a sour Stoic, a pleasant young Fellow;
And Airy be recompens'd well for that Favour,
If your Friend, in Return, should make him grow graver.
This Exchange should they make, it would set 'em both right;
Since one is too solid, and t'other too light.