Review the sentence:
Watching the second hand sweep the clock, Professor Grayson's boring
lecture on the French Revolution seemed as if it would never end.
Watching the second hand sweep the clock, a participle phrase, comes right before lecture, an illogical target. (Professor Grayson's, a possessive noun, functions as an adjective describing lecture.) Students, not the lecture, watch the clock!
Before you continue, review the rules for misplaced and dangling modifiers.