There are certain prognostics, too, that may be derived from water. If, when the sea is calm, the water ripples in the harbour, with a hollow, murmuring noise, it is a sign of wind, and if in winter, of rain as well. If the coasts and shores reecho while the sea is calm, a violent tempest may be expected; and the same when the sea, though calm, is heard to roar, or throws up foam and bubbling spray. If sea pulmones[1] are to be seen floating on the surface, they are portentous of stormy weather for many days to come. Very frequently, too, the sea is seen to swell in silence, and more so than when ruffled by an ordinary breeze; this is an indication that the winds are at work within its bosom already.