conjecture

And from thence I went to another place, which was still more horrible than the former, and I saw a horrible thing: a great fire there which burnt and blazed, and the place was cleft as far as the abyss, being full of great descending columns of fire: neither its extent or magnitude could I see, nor could I conjecture.

It is about forty furlongs [*1] in circumference, as far as one could conjecture.