"Now rest a bit--just as I am doing," I said; "don't move, but let your legs and body float up; just touch the grating with your arms stretched out, and as much of your body as possible under the water.  There, you see, you float like a cork.  Now you observe that, if you remain perfectly quiet, the water will float your body.  All the grating now does is to support your head; but if you were to turn on your back, and let your head sink down into the water, with only your face above, the water would support your head."