The'magic e' had not yet been invented, so he decided that, to distinguish between long and short vowels you would add a double consonant after every short vowel. So, (iff you wer writingng inn modderrn Ennglishsh) itt would look somthingng lik thiss. (My autocorrect did not like that sentence!)
I wonder why he didn't go for the more obvious solution of doubling long vowels? In which caas it wuuld luuk moor liik this. (I put two u's in look because oo is really a long u sound, not a long o sound.) Seems more logical to me.
Actually, putting a line over long vowels would be even nicer - and save ink. Sō it wūd lūk līk this. I think that wūd hav bēn a gūd solūtion.
Apologies to anyone reading this with a screen reader - I don't think it'll work!