Thee (Tityrus) the Pines, and every Vale,
  The Fountains, Hills, and every shrub did call: 

for by this the Concernment is express’d; and of the like nature is that of Thyrsis, in Virgil’s Meliboeus,

  {63} When Phyllis comes, my wood will all be green.

And this sort of Expressions is frequent in Theocritus, and Virgil, and in these the delicacy of Pastoral is principally contain’d, as one of the old Interpreters of Theocritus hath observ’d on this line, in the eighth Idyllium,

  Ye Vales, and Streams, a race Divine: 

But let them be so, and so seldom us’d, that nothing appear vehement, and bold, for Boldness and Vehemence destroy the sweetness which peculiarly commends Bucolicks, and in those Composures a constant care to be soft and easie should be chief:  For Pastoral bears some resemblance to Terence, of whom Tully, in that Poem which he writes to Libo, gives this Character,

  His words are soft, and each expression sweet.

In mixing Passion in Pastorals, that rule of Longinus, in his golden Treatise peri hypsous, must be observ’d, Never use it, but when the matter requires it, and then too very sparingly.

Concerning the Numbers, in which Pastoral should be written, this is my opinion; the Heroick Measure, but not so strong and sounding as in Epicks, is to be chosen. Virgil and Theocritus have given us examples; for tho Theocritus hath in one Idyllium mixt other Numbers, yet that can be of no force against all the rest; and Virgil useth no Numbers but Heroick, from whence it may be inferr’d, that those are the fittest.

{64} Pastoral may sometimes admit plain, but not long Narrations such as Socrates in Plato requires in a Poet; for he chiefly approves those who use a plain Narration, and commends that above all other which is short, and fitly expresseth the nature of the Thing.  Some are of opinion that Bucolicks cannot endure Narrations, especially if they are very long, and imagine there are none in Virgil:  but they have not been nice enough in their observations, for there are some, as that in Silenus.

  Young Chromis and Mnasylus chanct to stray,
  Where (sleeping in a Cave) Silenus lay,
  Whose constant Cups fly fuming to his brain,
  And always boyl in each extended vein: 
  His trusty Flaggon, full of potent Juice,
  Was hanging by, worn out with Age, and Use, &c.

But, because Narrations are so seldom to be found in Theocritus, and Virgil, I think they ought not to be often us’d; yet if the matter will bear it, I believe such as Socrates would have, may very fitly be made use of.