The " Chicago Daily Times " announces that one of the citizens of Michigan has discovered the cause and cure of the potato rot ; and that General Cass has certified to the fact. What that discovery is we are not informed. The " Times " does not appear to know that the same discovery has been and is now claimed by more than one citizen of New York. No certificate, however, will satisfy us ; we want to know what the diseovery is, and judge of it upon its own merits.