The learned Humboldt has said that, in the summer "when the sun entering the northern signs, rises towards the zenith, the breeze from the N.E. softens and at length ceases; this being the season at which the difference of temperature between the tropics and the continuous zone is least." He also states that the north polar supply of air ceases during this

season.

With every respect for such high authority, I cannot chime in with this opinion if it be meant to be taken literally. It seems to me that, the design of the process is, a change of air; and that there can be no suspension of that process whilst rarefaction goes on; which, there can be no doubt it does throughout the year. It is true that there exists but little difference at this season, between the temperature of the Temperate zone in continuity with the Tropic, but the effect would be, and indeed is according to observation, merely a lessening of the force of the N.E. trade wind.

According to the philosopher's words, a general calm must ensue, which we know is not the case. By the same parity of reasoning by which we account for the flagging of the N. E. Trade wind in summer, we arrive at the cause of its activity in the winter; but, the process of intermixture of airs is, I believe, carried on, principally, independent of wind.

Let there be ever so little difference in the temperature between the air within and without the tropic, the mixing will go on, and it is perpetuated, and regulated on one side by the amount of rarefaction, and the density of the atmosphere on the other side nearer the pole.

The mean lateral limit of the N. E. Trade wind* towards the equator is greater in winter, and less in summer; that is to say: the wind extends to about the 8th and a half degree north from April to August; and from November to March to about the 5th degree north.

But variations occur in these limits in different years; the difference of three and a half degrees between the summer and winter limit cannot therefore be relied on, the changes being regulated by causes which we cannot calculate upon; but, however complicated and inexplicable these may appear to us, we may safely believe that the natural system is perfectly regular.

The phenomenon of the S. E. trade wind over shooting its hemisphere and pushing on from two to five, and occasionally many more degrees north of the equator is very remarkable. What are the causes? The radi of the parallels are said to be greater in the south than in the north; and the sun is a trifle longer in the northern signs. Can these operate? Probably but little.

The presence of the equatorial current may be an assisting cause; and I think it by no means chimerical to infer that, the remarkable circumstances of the barrier of ice in the southern hemisphere being ten degrees of latitude nearer the equator than the belt of ice in the north is, may be an agent in the prolongation of this wind across the line.

Of the Atlantic.

From the information of a friend, a naval officer, I find that, when homeward bound, on the 1st of November 1826, he carried the S.E. trade wind to 70° 30′ N., in longitude 24° W. The wind then became variable with intervening calms, until the 6th, when he experienced N.E. and E.N.E. breezes to the 12th. The wind on that day changed to S.E., vacillating more easterly, and then veering to S. E. and south, up to the 16th in lat. 16° and long. 29°. After which the N.E. trade became steady. On the 14th the S.E. wind blew strong, with a heavy sea running! On the 20th, in 23° 10′ and 33° 46', the wind came from the westward, and so continued until the 24th, in 28° 58′ and 29° W., when it veered to N.N.E. The change of wind to the west had no effect on the barometer which was at 30.30; but it fell during the night of the 21st, when the wind blew in heavy squalls, and rose as the wind veered to the northward.

These mutations in the regular course of the N.E. trade whether we account for them from local causes acting on different strata of the atmosphere, or otherwise, appear as clear proofs that the velocity of the earth's rotary motion can have no mechanical effect on the air. The same officer, outward bound, in 1824, in May, carried the E.S.E. wind from the equator to 20° 02′ S. and long. 38° 11′ W. about two degrees from the Brazillian coast, when it veered to N.N.E. and continued to 30° S. and long. 46° W. The wind then came from the N.W., shifting to the south, and round again to the northward.

At the season of the year the wind is generally from the southward of the east point*; the instance given is therefore remarkable, and probably owed its origin to local causes; it is curious, inasmuch as the air was in motion from a lower towards a higher latitude, contrary, apparently, to calorific theory. In all such irregularities, it is desirable that in the progressive run, the state of the thermometer be regularly noted; the topt is a better place than the deck for its suspension. This northerly wind, it appears, was steady for 600 miles, flowing in a direction parallel with the general trend of the coast. How was the current running at the time? It is not mentioned; but here it is said to run with the wind. I am of opinion that currents often give a direction to light winds, the courses of which previously to reaching the current run towards, a different point.

Suppose the E.S. E. trade to approach the Brazil coast gently flowing, in reaching this implied current to the southward, it will turn from its E.S.E., course, and follow that of the water stream; so that the popular opinion is reversed, and reasonably, because it is not likely, unaided, that light wind would propel water into a stream; or turn it if flowing, in an opposite direction; a strong wind may turn it aside; but weak or fresh, alone it creates only a drift.

The seasonal changes in the direction of the S.E. trade wind may be

*What is called the southerly monsoon of the coast.

† Because there is less of the local atmosphere of the vessel or of radiation from the decks, &c., to affect the instrument.

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attributed to the sun's place. The drift current from the open ocean meeting with the resistance of the coast will be turned one way or the other; for, the water pressed onward will seek its level; in this case, the prevailing wind becomes operative, and the repelled water will go with it either to the southward, or the northward, according to the season. But, in the other instance, it was the season of the southern monsoon,' as it has been, perhaps, not very correctly, termed, when the northerly coast set is said to be established. If that was the fact, the current must have been running in opposition to the local N.N.E. wind; but I have assumed that, the stream was still running to the southward and so drew the wind with it. Of course no decision can here be given; but what I have said will show the propriety of seamen noting the direction of current as well as wind that the truth may be arrived at. Had the wind drew round to the northward from a more eastern quarter during the night only, then we might have hazarded a conjecture of the cause being the result of two contrary winds, the easterly from the ocean, and the westerly from the land; but it continued steady throughout for a distance of 600 miles. Calm is also often induced between the limits of the ocean breeze and the land-wind; and near islands the process of the renewal of the sea breeze is extremely curious, as if the land-wind had the effect of an opiate; in the evening, the Tropic wind gradually "goes off into a sound nap," in the morning, as though refreshed by its slumber, the air nearest the land begins to bestir itself, to breathe gently, and, crab like, "backing astern", until the potent power that rules it, having attained a few degrees of elevation, re-asserts its influence, it rushes in with a voice of gladness, dispensing its blessing far and wide.

To account for this N.N.E. wind, out of season, is not indeed an easy matter, but it is possible that during the rains (which set in in April) to the northward, the air had been greatly lowered in temperature by electrical discharges, and the increased activity of evaporation, whilst warm dry weather was prevalent to the southward, and rarefaction busy, hence a movement would follow from the lower to the higher latitude, so that the reversal of the ordinary course of operation would, as hinted, be only apparent. Some such cause probably occurs to create the Brazilian wind from the S.W., known by the local name of "Rebojos."

The old idea that wind always followed a rectilinear course is giving place to a new theory, the curvilinear. It is not, however, to be understood that the wind does never follow a straight course, but that it is often found to flow in a curve. Some of its movements are indeed very perplexing, as the causes are not cognizant to the senses: take, for instance, the often occurring phenomenon of its pendulum-like action, commencing at 1, veering regularly to 2, 3, 4, 5, and so on, and then as gradually returning from the last point to the first! As a single principle, or agent, calorific influence, so governing in ordinary cases; seems, as far as our knowledge and intelligence act, utterly inoperative.

The capriciousness of aerial currents, which has become a proverb, is a design; the result springing from their inconstancy in the extra-tropical regions of the earth, impresses us with that conviction, though we

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should fail in discovering the causes. The sun has been called the “god of the day"; it is also the god of the winds, but it has many subordinate agents in its service for the promotion of aërial agitation, and none perhaps more accessary in the government, than electricity.

Within the tropics wherever large islands lie in groups, they often influence the direction of the wind; but, calms are still more puzzling than the fluctuations of wind. What cause can be assigned for a column of air being in a state of quiescence between two opposite winds? Or, still more curious, a circle of calm in the heart of the trade wind! I have run with the trade wind (in the West Indies) gradually declining in strength, until the air became motionless, at least, apparently so; in a certain time after, a fresh breeze from the west pushed into this column of quiet air, and-What? Imparted to it a motion! That is questionable. What then drove the whole body to the eastward, merely causing it to shift its position, whilst the western stream of air pushed into its place! Who can decide? If another ship had been to the eastward, and we could have got a sight of her log subsequently, we should be better prepared to answer the question.

It may seem ridiculous, but some insight into these curious and interesting matters, may be gained by (under similar circumstances) ships chasing the wind! Had I been independent and could have ran back with this (temporary) west wind* on the same line, I had come, I should have found out what became of the calm, and whether, the trade wind fell back, as the blustrous west advanced its opposition to the east, or stood a "brush."

Had they been both of the same strength and met, what then? Greek against Greek! "and the tug of war!" Even, so, probably, a gale, with a strong tendency to a circular motionel electricity forming the ring, whilst the helpless calm would be shut up in the centre, as in a glass case, and the very genï would be weeping for joy! This would be, we think, very like an insipient hurricane.

In these aerial contests, as, sometimes, in gladiatorial combats, the stronger, though prevailing for a time, ultimately, from exhaustion, yields to its weaker opponents.

The interloping west wind I have spoken of, after a brief bluster, and a scowl that was enough to create alarm "beat its march back," but how far it had pushed its advance, I cannot say, it, however, began to breathe short, as the fancy would say, became "winded;" which symptom no sooner showed itself, than the old trade, peeped in side ways, and finding its opposer at the last gasp, gained "pluck," and so threw in "right and left" (variable squalls), and after occupying an hour or two "crowing" over the defunct, came sliding in, and whistling its usual tune, as complaisantly as if nothing had happened to interrupt its wonted equanimity.

I have often laughed at the idea of how close a resemblance may be made between these aërial doings, and the actions proceeding from the

* It could not have gone far, as it lasted but a short time.

capricious workings of the human heart! This strain may be very undignified, and very poor philosophy, true it may be; but, it is more, it is true.

"Philosophy is not science," so it is said; I have nothing to do with the question: what I wish, and have a great desire to see, is, the practical seaman of deep thought, habitually become observant of natural phenomena; and not only record the facts, but state his opinions freely, a single good idea may sometimes be found among much matter that is of little value, and thus without any pretensions to subtilty in science, he may be useful to it.

I am in this chat, merely skimming the surface here and there with hasty wing. But, to proceed:

The variations in the northern limit of the N.E. trade of the Atlantic are inferred to be consequent on the sun's place: but even in one season there are variations in the general line. The received opinion is that, when the sun is in the southern signs the general line is about the 27th degree north; and, in the reverse season it reaches as high as the 30th, and 32nd degrees. It would seem, however, that the variations of this line, are not solely influenced by the sun's place, for, if the luminary alone acted, the general line would change with regularity, which is not the case.

Two ships crossing the tropic under the same longitude, one a year after the other, on the same day of the month, will find a difference of one, two, or three degrees of latitude in this line; and two vessels crossing southerly, but under different meridians, in the same day, will meet with the settled trade in different parallels; but there is not a doubt that the sun has a governing influence on the extension of the action of this wind in the different seasons. I have as little doubt, too, that the general character of the atmospheric temperature of the Boreal regions has something to do in the process, but even in that we must fall back upon the sun and the seasons.

There is a belt northward of the tropic of Cancer, and southward of the latitudes, wherein the westerly winds are prevalent, which has been termed by seamen "The Variables", being a sort of neutral space between the N.E. trade and westerly winds. Within this belt the temperature varies little from that of the tropic line, and calms, and light fluctuating breezes are therein prevalent. These features seem to be derived from the position of the space being intermediate of the two winds moving in opposite directions; and the local atmospheric changes going on within it, must in some degree influence the bordering currents of air on either side, perhaps this may give a clue to the local variations which occasionally occur in the northern line of the trade wind.

Another remarkable circumstance is that, the trade winds commence at a certain distance from the western face of the continents, between which and the starting line, there are westerly, and cross winds; along the western line of South America it is well known that a southerly wind exists.

In the Great Ocean (by no means a "Pacific" one) there are also