In ordinary circumstances in our latitude, the winds are generally regulated by the differences in pressure induced by contrasts between continents and oceans. Where the air becomes heated, an area of low pressure is produced, the warm air becoming rarefied and ascending, and the heavier cold air rushing in from the sides to supply its place. In winter, the weather over these islands is controlled to a great extent by the winds which sweep round a large area of depression which exists over the Atlantic, the mean centre of which is about midway between the continents of Europe and America, in the latitude of the Orkney Islands. This depression is the result of the contrast produced between the comparatively warm air over this portion of the Atlantic and the much colder air over the northern portion of Europe and America, which is continually flowing in to supply the place of the lighter and constantly ascending warm air. The winds sweeping round this centre strike our shores from the south-west. This depression is not stationary, but is continually shifting over a large but well-defined area, and it gives rise to many subsidiary eddies, or small cyclone systems as they are called, which sometimes skirt our coasts, or travel over these islands, bringing with them the storms of wind and rain and sudden changes of the wind with which we are familiar. In spring, the prevailing winds from the east and north-east, so much dreaded by many, are the result of a large cyclonic system formed by the sudden increase of temperature over middle and southern Europe, as the sun’s rays gain strength and the days lengthen. The temperature is not yet sufficiently high to bring in the air from off the Atlantic, as happens when the season is further advanced, so that the cold air rushes in from the polar regions in a huge eddy, striking our coasts from the east and north-east, and bringing in its train all the attendant miseries which make our English spring a time to be dreaded by the weak and ailing.