The first is a good spondeus, the second a good iambus, and if the same wordes be broken thus it is not so pleasant.
  I`n e-x tre-ame de` sire

And yet the first makes a iambus, and the second a trocheus ech sillable retayning still his former quantities.  And alwaies ye must haue regard to the sweetenes of the meetre, so as if your word polysillable would not sound pleasantly whole, ye should for the nonce breake him, which ye may easily doo by inserting here and there one monosillable among your polysillables, or by changing your word into another place then where he soundes vnpleasantly, and by breaking, turne a trocheus to a iambus, or contrariwise:  as thus: 
  Ho-llo`w va-lle`is u-nde`r hi-e`st mou-ntai`nes
  Cra-ggi`e cli-ffes bri`ng foo-rth the` fai-re`st fou-ntai`nes

These verses be trochaik, and in mine eare not so sweete and harmonicall
as the iambicque, thus: 
  The` ho-llo`wst va-ls li`e u-nde`r hi-e`st mo-unta-ines
  The` cra-ggi`st clifs bri-ng fo-rth the` fai-re`st fou-nta-ines.

All which verses bee now become iambicque by breaking the first
bissillables, and yet alters not their quantities though the feete be
altered:  and thus,
  Restlesse is the heart in his desires
  Rauing after that reason doth denie.

Which being turned thus makes a new harmonie.
  The restlesse heart, renues his old desires
  Ay rauing after that reason doth it deny.

And following this obseruation your meetres being builded with polysillables will fall diuersly out, that is some to be spondaick, some iambick, others dactilick, others trochaick, and of one mingled with another, as in this verse.
  He-aui`e I-s the` bu-rde`n of Pri`nce`s i-re

The verse is trochaick, but being altered thus, is iambicque.
  Fu`ll he-aui`e i-s the` pa-ise o`f Pri-nce`s i-re

And as Sir Thomas Wiat song in a verse wholly trochaick, because the
wordes do best shape to that foote by their naturall accent, thus,
  Fa-rewe`ll lo-ue a`nd a-ll thi`e la-wes fo`r e-ve`r

And in this ditty of th’Erle of Surries, passing sweete and harmonicall: 
all be Iambick.
  When raging loue with extreme paine
  So cruell doth straine my hart,
  And that the teares like fluds of raine
  Beare witnesse of my wofull smart.

Which beyng disposed otherwise or not broken, would proue all trochaick, but nothing pleasant.

Now furthermore ye are to note, that al monosyllables may receiue the sharp accent, but not so aptly one as another, as in this verse where they serue well to make him iambicque, but not trochaick.
  Go`d grau-nt thi`s pea-ce ma`y lo-ng e`ndu-re