From the first one:
"bear" - I can make better sense of what follows if it's "hear", but as a misspelling of "here".
I like your suggestion there. Also: one has to keep in mind, that the punctuation is more or less missing. In that way a full stop behind »bear« is possible too.
So the sentence could go even in the way of: »…by which this conversion of wood into stone <verb> here[.] the first impression left upon the mind…«
Another thought, which involves a gross misreading, is that 'scites bear' is actually 'takes place'. (s=t, ci=a, t=k; b=p, e=l, r=ce)
One of these confusions in a word might be easily spotted, but here it would mean having a whole lot of them all together. I wonder...?