During the frequent violent gales of last autumn, the author had remarked the excessive fluctuation of the barometer; and following up this phenomenon by means of the portable aneroid barometer, he found that not only was this fluctuation dependent on the wind and on the barometer being in a screened position; but that accompanying the fluctuation was a constant depression increasing in amount with the velocity of the air, and that this depression amounted in strong gales to a larger quantity than all the other usual corrections applied to a barometrical reading; and must be applicable to all the ordinary positions where barometers are observed, whether by sea or land.