to reserve them for your greatest necessities: when you cannot extricate your hero by any human means, or yourself by your own wit, seek relief from Heaven, and the Gods will do your business very readily. This is according to the direct prescription of Horace in his Art of Poetry.
Nee deus intersit, nisi dignus vindice nodus
Inciderit.
That is to say, a poet should never call upon the Gods for their assistance, but when he is in great perplexity.
For the Descriptions.
For a tempest. Take Eurus, Zephyr, Auster and Boreas, and cast them together in one verse: add to these of rain, lightning and thunder (the loudest you can) quantum sufficit. Mix your clouds and billows well together till they foam, and thicken your description here and there with a quicksand. Brew your tempest well in your head, before you set it a blowing.
For a battle. Pick a large quantity of images and descriptions from Homer's Iliad, with a spice or two of Virgil, and if there remain any overplus, you may lay them by for a skirmish. Season it well with similes, and it will make an excellent battle.
For a burning town. If such a description be necessary (because it is certain there is one in Virgil) old Troy is ready burnt to your hands. But if you fear that would be thought borrowed, a chapter or two of Burnet's Theory of the Conflagration, well circumstanced and done into verse, will be a good succedaneum.
