John shut off both engines, and they began to volplane down in a great stillness, sailing like an immense hawk.  Lower and lower they went--fourteen, thirteen, twelve, eleven, ten thousand feet.  Now they were gliding through clear, thin air; now cutting a hole through a heavy cloud so impregnated with moisture that it sweat over the glass and the boys would have to wipe a sleeve across hastily to improve the vision.  Eight, seven, six, five, four, three, two!