It is in vain to leave this to the Reader's imagination: --to form any kind of hypothesis that will render these propositions feasible, he must cudgel his brains sore, --and to do it without, --he must have such brains as no reader ever had before him. 
It is in vain for the Reader to try to understand this: to form any theory that will explain it, he must cudgel his brains sore. 