Because in such a wilderness of running rigging, whose various different relations aloft cannot always be infallibly discerned by what is seen of them at the deck; and when the deck-ends of these ropes are being every few minutes cast down from the fastenings, it would be but a natural fatality, if, unprovided with a constant watchman, the hoisted sailor should by some carelessness of the crew be cast adrift and fall all swooping to the sea.