therewith > with that; thereupon at once > simultaneously; immediately
2 Their fluttering arrows, thick as flakes of snow, 3 And round about him flock impetuously, 4 Like a great water flood that, tumbling low 5 From the high mountains, threats to overflow
threats > threatens
6 With sudden fury all the fertile plain, 7 And the sad husbandman's long hope does throw 8 Adown the stream, and all his vows make vain,
Adown > Down vain > futile
9 Nor bounds nor banks his headlong ruin may sustain.
Nor > Neither his > its (the flood's); his (the husbandman's) ruin > downfall (of the water or the husbandman) sustain > withstand
211.19
Vpon his shield their heaped hayle he bore,
2 And with his sword disperst the raskall flockes,
Which fled a sunder, and him fell before,
4 As withered leaues drop from their dried stockes,
When the wroth Western wind does reaue their locks;
6 And vnder neath him his courageous steed,
The fierce Spumador trode them downe like docks,
8 The fierce Spumador borne of heauenly seed:
Such as Laomedon of Ph{oe}bus race did breed.
1 Upon his shield their heaped hail he bore, 2 And with his sword dispersed the rascal flocks, 3 Which fled asunder, and him fell before, 4 As withered leaves drop from their dried stocks