the country before I noticed, in the far distance, a singular arch of light cloud, which lay about 20° above the horizon, exactly in the direction we were proceeding, that is, nearly due south-west of us. As we progressed on the journey the arch rose higher and higher above the horizon, so that in about two hours its summit approached the zenith of the spot where we then were, and beneath it was a pale, lavender-blue sky, quite devoid of cloud.

After awhile, when our train reached Ringwood junction, only a short distance from Bournemouth, we passed right under the arch of cloud, the summit being then at a great elevation in the atmosphere; and as we did so, we were sensible of having passed into quite a different climate; we had come, if I may so express it, from a season of Spring, into one of Summer. One of the feet of the arch appeared to rest on the land somewhere beyond Ringwood, and the other over the sea, on the Isle of Wight. This singular" cloud-arch" remained perfectly still, apparently, during the whole evening. Next day, I saw nothing of it.

This is what Goethe says of a similar observation in Sicily:

Girgenti, 27th April.-Standing by the side of the sea, my attention was attracted by a long streak of cloud over the southern horizon, like an immense chain of mountains. These clouds indicated the African shores. Another phenomenon appeared to me still more singular; it was light cloud forming a vast half circle, leaning on one side on the soil of Sicily, rising boldly into a clear blue

I

CHAPTER XIX.

Influence of the Gulf Stream on the State of the Atmosphere over Europe and the Atlantic-The Curve of Average Temperature and its Teachings.

THE influence of the Gulf Stream upon the state of the atmosphere over Europe and the Atlantic Ocean has been vividly brought to light, more especially by the indefatigable labours of Maury. This immense current of warm water is referred to several causes, the principal of which is the tendency of the warm tropical waters to flow towards the poles, their high temperature making them lighter than the waters of the colder regions. The direction of the current is due, partly, to the rotation of the globe, which naturally deflects towards the east both the winds and the ocean currents.

Leaving the Gulf of Mexico, whence it derives its name, and passing the Straits of Florida, the Gulf Stream flows through the canal of the Bahamas, and pours itself into the Atlantic Ocean, where its waters preserve, for thousands of miles, their high temperature, and their direction towards the north. In the Gulf of Mexico this temperature is about 75° Fahr.; and when it merges into the Atlantic about 72° Fahr.

some twelve degrees higher than that of the Ocean in the same latitude. When it has flowed over ten degrees of latitude, still further north, it has only lost about 4° of heat; and after a course of 3000 miles, in a northerly direction, it still preserves, even in the depth of winter, the mild temperature of summer.

Thus it arrives at the 40th parallel of north latitude, and then, spreading out, it covers many thousands of square miles, bestowing upon this vast surface its congenial warmth. Meeting with the banks of Newfoundland, where it gives rise to dense fogs which are so dangerous to navigation in winter, it deviates towards the east, and continues its course with less impetuosity, until it reaches the British Isles. There it divides into two branches, one continuing towards the north to the polar basin of Spitzbergen, whilst the other, flowing down the English coasts, throws itself into the Gulf of Gascony, both branches preserving a temperature several degrees higher than the ocean.1 Its influence on the Orkney Islands is such that although situated at 60 north latitude, ponds rarely freeze in winter, and the climate of Liverpool, for instance, which is more northerly than Newfoundland, is quite mild and agreeable; whilst Labrador, which corresponds to England on the American coast, is almost uninhabit able. If the temperature and velocity of the Gul Stream were the same at 200 fathoms as at the surface the quantity of heat evolved from its waters into th

1 Ships that are covered with snow and icicles experience the effect of a rapid thaw the moment they enter the waters of the Gulf Stream

Atlantic would, according to Maury, suffice to raise from freezing-point to summer temperature the entire bulk of the atmosphere lying over Great Britain and France.

Most of the atmospheric perturbations of the Atlantic Ocean can be traced to the influence of the Gulf Stream. Not only the fogs of Newfoundland, but the disastrous tempests of wind, or hurricanes, which occasionally blow in certain parts of the Atlantic, appear to be due to the difference of temperature between the waters of this vast current and those which surround it. Storms have been traced from the west coast of Africa and followed across the ocean until they meet with the waters of the Gulf Stream, when, instead of continuing their straight course, they suddenly change their direction, and blow again across the Atlantic, till they reach the coasts of Europe, marking their trajectory by a series of calamities.

The mild climate of the British Isles is very greatly due to this immense current of warm water, without which we should be no better off, in this respect, than people who live in the Arctic circle.

There can be little doubt that, as there exist in the Earth's atmosphere, fluctuations of temperature, of electricity, of barometric pressure, and of magnetic force, this vast stream of warm water may, also, have its periodical fluctuations of quantity, or temperature, and I am of opinion that it may thus affect what is known as the curve of average temperature.

After a careful consideration of this curve of average