atwixt > between; hence: also, mixed in
3 And an earthquake, as if it straight would loose
straight > straightway, immediately
4 The world's foundations from its centre fixed;
centre fixed > [fixed centre]
5 A direful stench of smoke and sulphur mixed
direful > terrible, dreadful
6 Ensued, whose noyance fild the fearful stead
noyance > annoyance fild > filled; or: defiled (cf. 105.32:2 etc.) stead > place
7 From the fourth hour of night until the sixth;