Could a historiographer drive on his history, as a muleteer drives on his mule, --straight forward; ----for instance, from _Rome_ all the way to _Loretto_, without ever once turning his head aside either to the right hand or to the left, ----he might venture to foretell you to an hour when he should get to his journey's end; ----but the thing is, morally speaking, impossible: For, if he is a man of the least spirit, he will have fifty deviations from a straight line to make with this or that party as he goes along, which he can no ways avoid. 
Could a writer drive his history straight forward, as a muleteer drives on his mule, without ever once turning his head either to right or left, he could foretell to the hour when he should get to his journey's end; but the thing is, morally speaking, impossible. For, if he is a man of the least spirit, he will have fifty deviations to make as he goes along, which he cannot avoid. 