Moby-Dick Questions Ch. 35: What three things do masthead standers

What three things do masthead standers look for?  What happens to you while standing on the masthead?  Why is Ishmael a lousy masthead stander?  Why doesn’t the Platonist spot any whales?  What do “Descartian vortices” and “pantheistic ashes” have to do with looking for whales?  (173 [136])