Sentence:  For we are not here to understand, as perhaps some have, that an author actually falls asleep while he is writing. It is true, that readers are too apt to be so overtaken; ...To say the truth, these <WSD>soporific</WSD> parts are so many scenes of serious artfully interwoven, in order to contrast and set off the rest; 
Meaning of the word marked with <WSD> tags:  Tending to induce sleep.