Chapter VI (2)

DEAR SIR,--Understanding you are desirous of collecting curious
meteorological facts, I take the liberty of communicating to you what
I saw in the month of December, 1815, at the Island of Owhyhee. I lay
at that island in the Cavrico Bay,[3] in which Captain Cook was
killed, three weeks, and every day during that time, very soon after
the sea breeze set in, say about nine o'clock, a cloud began to form
round the lofty conical mountain in that island, in the form of a
ring, as the wooden horizon surrounds the terrestrial artificial
globe, and it soon began to rain in torrents, and continued through
the day. In the evening the sea breeze died away and the rain ceased,
and the cloud soon disappeared, and it remained entirely clear till
after the sea breeze set in next morning. The land breeze prevailed
during the night, and was so cool as to render fires pleasant to the
natives, which I observed they constantly kindled in the evening. I
was particularly struck with the phenomena of the cloud surrounding
the mountain, when none was ever seen in any other part of the sky,
and none then till after the sea breeze set in, in the morning, which
it did with wonderful regularity. The mountain stood in bold relief,
and its top could always be seen from where the ship lay, above the
cloud, even when it was the densest and blackest, with the lightning
flashing and the thunder rolling, as it did every day. I passed up
through the cloud once, and I know, therefore, how violently it
rains, especially at the lower side of the cloud. This rain never
extends beyond the base of the mountain;[4] and all round the horizon
there is eternally a cloudless sky. The dews, however, are very
heavy, and there seems to be no suffering for want of rain. That this
state of things continues all the year, I have no doubt, from what an
American, by name Sears, who had spent four years there, told me; he
had seen no change in regard to the rain.

CALEB WILLIAMS.

Providence, R. I.

Similar citations might be made to show that the sea breeze is induced by the same cause which forms the clouds over the land--that it is frequently wanting for three or four days under a vertical sun, and that the land breeze blows gently and not with corresponding force where there is no surface trade, or where it is deflected, not reversed.

A succession of showers passing across the country to the north, within one hundred to one hundred and fifty miles, almost always produces a southerly wind to the southward of them. There is more that is peculiar about these belts of showers. Although they consist of large highly-electrified cumuli, there is a strong tendency to cirro-stratus condensation in the lower part of the trade over them; and it is that condensation rather than the cumuli, which attracts the surface atmosphere from the south. They would be storms, if the atmosphere had not a summer-tropical tendency to showers. There is, too, a tendency in these belts to extend to the south, and it is generally, as far as I have observed, the extension southerly of those belts, by the formation of new showers which terminate the "hot spells" or "heated terms" of mid-summer. The very oppressive and fatal one of the summer of 1853, was, in character, a type of all--although exceeding them in severity. The first three or four days were calm, hot, and smoky--an appearance which attends all similar periods more or less, refracting the red ray of the light, and giving the sun a peculiar dry-weather, red appearance. (This smoky haze is usually atmospheric, and occasionally seen even in March, although not unfrequently fires in the woods fill the air with actual smoke, and very much increase it, and when this is so, the odor of the smoke is often perceptible.) Then we began to have a fresh south-west by south breeze in the day-time, hauling to the south-west, and dying away at nightfall. The next day, the tendency to condensation and consequent belt of showers having extended further south and approached nearer to us, the S. S. W. wind blew _fresher_ toward it, and _did not die away at nightfall_. During the evening the reflection of the lightning playing upon the tops of the thunder clouds, just visible at the north (heat-lightning, it is termed, because supposed to be unaccompanied by thunder, but in reality lightning reflected from clouds at too great a distance for the thunder to be heard), and the continuance of the southerly wind after nightfall, gave sure evidence of the coming showers the next day, and an end of the excessive heat for that time. So ended both of those long-to-be-remembered "heated terms" of 1853.

The same is probably true of the interior of the country every where. Lieutenant Maury, in the course of his investigations, and in order to ascertain the direction of the winds in the Mississippi valley during rain, addressed a number of gentlemen, and received their replies, which are published with his wind and current charts. Several answered, among other things, that, "whenever the lightning appears to linger at the north at eventide, rain almost invariably follows speedily; not so in the south." Thus it frequently is with us. If, during a hot, dry time, of a few days continuance, the lightning so lingers in the evening, and the wind continues to blow _fresh_ from the southward _after nightfall_, showers will generally follow within forty-eight hours, most commonly the next day, and a cool N. N. W. or N. W. wind with a favorable change ensue. Such, at least, has been the result of my observation for many years.

Indeed this seems to be the general law in summer in the Mississippi valley, where the easterly winds are not so common as with us. To illustrate this further, I copy from a recent work by T. Bassnett, entitled the "Mechanical Theory of Storms," two short extracts, showing the manner in which belts of showers extend southerly, while progressing north-eastwardly, at Ottawa. The first occurred in August, 1853; the last, December, 1852. The first was a belt of showers; the latter would have been in August, but the lateness of the season changed its character somewhat, though not entirely, to a more regular rain, especially toward the close.

"AUGUST 6th.--Very fine and clear all day: wind from S. W.; a light
breeze; 8 P.M. frequent flashes of lightning in the northern sky; 10
P.M., a _low bank of dense clouds in north_, fringed with cirri,
visible during the flash of the lightning; 12 P.M., same continues.

"7th.--very fine and clear morning; wind S. W. moderate; noon, clouds
accumulating in the northern half of the sky; _wind fresher_, _S.
W._; 3 P.M., a clap of thunder over head, and black cumuli in west,
north, and east; 4 P.M., much thunder and scattered showers; six
miles west rained very heavily; 6 P.M., the heavy clouds passing over
to the south; 10 P.M., clear again in north.

"8th.--Clear all day; wind the same (S. W.); a hazy bank visible all
along on _southern horizon_.

"DECEMBER 21st, 1852.--Wind N. E., fine weather.

"22d.--Thick, hazy morning, wind east, much lighter in S. E. than in
N. W.; 8 A.M., a clear arch in S. E. getting more to south; noon,
_very black in W. N. W._; above, a broken layer of cirro-cumulus, the
sun visible sometimes through the waves; wind around to S. E., and
fresher; getting thicker all day; 10 P.M., _wind south, strong_;
thunder, lightning, and heavy rain all night, with strong squalls
from south.

"23d.--Wind S. W., moderate, drizzly day; 10 P.M., wind west, and
getting clearer."

It is obvious that the showers at the north passed east on the evening of the 6th of August; that new showers, taking the same course, originated in the north, but more southerly next day, with S. W. wind, and that they passed east, and others formed successively further south, which passed over the place of observation late in the afternoon, and that others formed south and passed east during the night and next day, visible in a bank on the southern horizon.

Later or earlier in the spring and autumn, these brisk afternoon southerly winds continuing after nightfall, indicate moderate rains from a rainy belt extending in a similar manner, without the cumuli and thunder which attend those of mid-summer. I shall recur to this class of showers and storms when we come to their classification.

Light surface winds from south-west to west are not often storm-winds, and are usually those which the trade near the earth draws after it. Sometimes the trade seems to draw the surface wind from the S. W. and W. S. W. with considerable rapidity, and some scud a little distance above the earth. When this is so, it will be found that a storm has passed to the north of us, or a belt of rains is passing north, which may or may not have sufficient southern extension to reach us. When there have been heavy storms at the south in the spring, especially if of snow, the S. W. wind which the trade draws after it, and which comes from the snowy or chilled surface, is exceedingly "raw"--that is, damp and chilly, although not thermometrically very cold. Probably every one has noticed these "_raw_" S. W. winds of spring.

Usually, when storms and showers, which have not a southern lateral extension, pass off, the trade is very near the earth, and a light S. W. wind or calm follows for a longer or shorter period. Not unfrequently, however, our N. E. storms terminate with a S. W. wind, shifting suddenly, perhaps, just at the close of the storm, during what is sometimes called a "clearing-off-shower," or, more frequently, dying gradually away as a N. E. wind, and coming out gently from the S. W., following the retreating cloud of the storm. In such cases it is said to "clear off warm."

With us the wind rarely blows from the west, except while slowly hauling from some southerly point to the N. W. It is probably otherwise east of the lakes and in some other localities to the north-west.

Occasionally, and most frequently in March, a W. to W. N. W. wind follows storms, and blows with considerable severity, with large irregular, squally masses of scud, and sometimes a gale. Such was the character of the dry gale which crossed the country, particularly Northern New York, in March, 1854, doing great damage. These westerly winds are always accompanied by a continued depression of the barometer, and peculiar, foggy, scuddy, condensation, and should be distinguished with care from the regular and peculiar N. W. wind, as they may be, by the continued depression of the barometer, and the character of the scud. They are doubtless magnetic storms.

The remaining surface wind, the N. W., the genuine Boreas of our climate, the invariable fair-weather wind, is one of great interest. It is unique and peculiar. It is not the left-hand wind of a rotary gale, and has no immediate connection with the storm. I have known it blow moderately, fifteen successive days in winter; rising about ten A.M., and dying away at nightfall. Occasionally, but very rarely indeed, a light wind exists from the N. W. during a storm, owing probably to a focus of intensity in relation to some surface the storm covers, like the focus which exhibits itself as a clearing-off shower near the close of a storm; but the real fair-weather Boreas is a different affair altogether. Let us observe with care its peculiarities; they are instructive.

1st. It rarely blows with any considerable force beneath the trade while there are storm clouds, or any considerable condensation in it. It does not interfere with that reciprocal action which takes place between the trade and the earth, during approaching or existing storms. I have frequently seen it with its peculiar scud clouds in the N. W., waiting for the storm condensation of the trade to pass by, that full of positive electricity it might commence its sports; rushing and eddying along the surface, licking up the warm, south polar, electric rain, which stood in pools upon the ground, or rose in steamy vapor from the surface, and with its cool breath dry up the muddy roads as no degree of heat can dry them.

The annexed figure (14) shows the appearance of the northern edge of a stratus storm cloud, passing off E. N. E. at the close of the storm, which was "_clearing off from the north-west_." It is from a daguerreotype view, looking W. N. W., taken at eight o'clock in the morning, in the fall of the year. Near the horizon maybe seen the N. W. scud, forming in the N. W. wind, which is about to follow the retreating edge of the storm cloud.

Figure 15 is from a daguerreotype view, taken at eleven o'clock the same day, when the storm cloud had passed off and its edge remained visible only south of the zenith, and the north-east scud had risen up and covered the northern half of the sky, and the wind was blowing a gale from that quarter.

Another view was taken about two P.M. of the same day, when the scud had a very dark, gloomy appearance--as _dark_ and _gloomy_ as those of a Mexican norther--too dark to represent by a cut.

Not unfrequently in a moist summer season, after a day of showers or rain, which have had an extending formation or lateral extension from north to south, it will commence blowing in the morning, and encourage the hay-maker with the hope of fine weather. But often before noon, the milky stratus condensation above with cumuli below, will appear in the trade; the N. W. wind die away and variable airs from the east or south appear, to be followed toward night by an enlargement of the cumuli and showers. It rarely, if ever, blows fresh till the storm condensation of the trade has passed; or continues to blow after that condensation reappears. When it commences blowing after a storm, and the northern edge of the storm is not over us, we may frequently see the latter low down in the S. E. passing eastward.

2d. Its scud are peculiar. Every one, probably, has noticed them. They are distinct, more or less disconnected, irregular, with every form between those of the easterly scud, cumulus, and stratus, according to the season. If large, with _dark under surfaces_; forming _rapidly_ and as _rapidly dissolving_; rarely dropping any rain, sometimes dropping a flurry of snow, in November or March, oftener than at any other period; sailing away to the S. E., and casting a traveling shadow as they pass on over the surface of the earth. Their electricity, particularly when white, is probably always positive, as that of all whitish clouds is supposed to be.

3d. _It is emphatically a surface wind._ The incident storm winds, the N. E. and S. E., frequently _commence blowing_ under the storm, toward its point of greatest intensity, _up near the line of cirro-stratus condensation_, evidenced by the running scud; or blow there with most rapidity, and so continue for hours before the whole surface atmosphere from thence to the earth becomes involved in the movement; and sometimes without being felt below at all. Not so with the N. W. wind; it _begins at the surface_ and blows there with more rapidity than above; it seems to be attracted by the earth; it interposes between the earth and the trade, wedging the trade up and occupying its place. It blows under at all seasons of the year, but most readily and strongly from a surface of snow whose electricity is always positive. Hence it blows most strongly and _continuously_ when snow has fallen at the north, and prevails during winter very much in proportion to the extent and continuance of the covering of snow which invests the earth in that direction. It follows after storms, and particularly warm rains, during the autumn, winter, and spring months, which have a lateral southern extension. Whether it is increased by the snow from the surface from which it blows, or is caused by the same magnetic action which causes the great fall of snow, is a question we shall consider hereafter.

4th. It does not connect or mingle with the trade current in any way, or change or divert the course of that current; but interposes between it and the earth, elevating the trade in proportion to its own volume, above the influences of the earth (when the trade becomes free from condensation, and singularly, clear); and raising _proportionately_ the barometer. An experienced observer can frequently estimate, with considerable accuracy, the rise of the barometer, by measuring with his eye, (when the clouds will enable him to do so,) the depth of this interposed N. W. current. The barometer rarely rises after a storm, for twenty-four or forty-eight hours if the wind continues at any point from S. W. to W. N. W., but always rapidly as soon as the genuine N. W. current with any considerable depth interposes and elevates the trade.

It will be obvious to every one, I think, certainly, if they will hereafter study the subject and observe for themselves, that the N. W. wind does not blow away the storm; and that it follows after it, blowing over the surface which is uncovered by the storm; rarely, if ever, with any force when the body of the storm passed south of us; and that it is a purely surface wind, seemingly attracted by the peculiar magneto-electric state in which the surface of the earth is left, compared with a snow-clad surface to the north, by a recent storm, or that peculiar state of the trade which is left by the action of the storm. It seems to follow that magnetic wave which, passing from north to south, acts in its course upon the counter-trade, producing the storm, or belt of showers, and giving them their southern lateral extension, and will well repay future telegraphic investigation. Its electricity is intensely positive--that of the earth by the action of the storm as intensely negative.

5th. This N. W. wind occurs in all parts of the northern hemisphere, so far as we have data to determine, and its corresponding wind from the S. W. occurs in the southern hemisphere. It is identical with a class of the northers of the Gulf of Mexico, as a brief analysis of the character of the latter will show.

1st. The fall and winter _norther_ is a dry wind without rain or falling weather--so is our N. W. wind.

2d. It is preceded by a falling barometer; S. E. scud and rain at the point where it blows, or to the eastward of it. So is ours when it blows a gale in the fall and spring months, which bear the nearest resemblance in climatic character to the periods when the northers blow. With this distinction, however, that our precedent rains either pass over us or to the southward, the direction of storms being E. N. E.; their precedent storms passing over or to the eastward of them as they move more to the northward.

3d. It is often preceded by a copious dew; so is ours--such dews often following light fall rains in our climate, and preceding N. W. wind.

4th. The most peculiar characteristic, however, is that the barometer rises rapidly and invariably while the norther prevails, and very much in proportion to its violence. The same is true of our genuine N. W. wind, and is not true _of any other wind_ on this continent which I have observed or read of.

5th. While they are thus alike in these respects, they are unlike in no respect.

Mr. Redfield has traced them in _supposed_ connection with storms which continue from that vicinity across the United States to the E. N. E., and endeavored to connect them with those storms, as the left-hand winds of a rotary gale. Obviously, I think, they are identical with our N. W. winds which also _follow_, indeed, but _are distinct from the storms_.

There are a class of northers in the Gulf of Mexico--the "Nortes del Muero Colorado"--sometimes occurring in the summer months, beginning at N. E., veering about and settling at N. N. W., and as they decline hauling round by the west to the southward. These winds correspond precisely with the hurricane winds of the West Indies, and are doubtless the incident winds of a storm traveling thence to the N. N. W. precisely as our N. E. or E. N. E gales are incident storm winds to the N. E. storms of our latitude.

In this connection we will look at the peculiarities of a West India hurricane.

"It is not a little remarkable," says Mr. Espy, speaking of the storms and hurricanes of the West Indies, "that all these storms, and _all others which have been traced to the West Indies_, traveled N. W. almost at right angles to the direction of the trade-wind in those latitudes, but very nearly, if not exactly, in the direction of an upper current of the air known to exist there toward the N. W." Substantially the same facts have been repeated by Mr. Redfield, and demonstrated by his able investigations, both there and in the Eastern Pacific, and are confirmed by the observations of Edwards, Lawson, and others, while residents there. It is a matter of surprise that gentlemen like Messrs. Redfield and Espy, who have certainly displayed great ability in the investigations of meteorological phenomena, should fail to recognize a more intimate relation between this upper current and the storms they were investigating, and to detect the general laws which govern both. The storms and hurricanes of the West Indies are comparatively of small diameter, and have little advance condensation. When they pass on to the south-western portion of North America and curve to the N. E., as they frequently do, they enlarge in front and at the sides, and their advance condensation, which is not dense enough to drop rain, extends in some cases from one to three hundred miles; and the storm itself, by the time it reaches the Alleghanies, may extend one thousand to fifteen hundred miles, and perhaps in certain magnetic states of the surface, and occasionally, may cover the entire portion of the continent, from north to south. Such, probably, was very nearly the extension of the storm investigated by Professor Loomis. In the West Indies, however, at the commencement, they vary from twenty to one hundred miles, or possibly more, in width.

First, they are preceded by a hot, sultry and oppressive atmosphere--_as are electric storms every where_--a peculiar electric state of the earth and adjacent air.

Second, the black clouds and lightning which indicate the approaching hurricane are seen to the S., S. E., and E. S. E., according to the season of the year, as we see them at the westward. During the rainy season, and when the storm, as is usual at that period, is small, and the S. E. trade blows more eastwardly, the wind at the Windward Islands, possibly, may set in at the north, and back round by the east as it progresses. So Colonel Reid thinks it sometimes does, at Barbadoes. But when the belt of rains is south, and the hurricane comes from the south-east, and is larger and more violent in its action, and the north-east winds prevail, the first effect is an increase of these trades. Soon, however, the wind hauls to the north and north-west, in opposition to its course, bearing the same relation to it that our east and north-east winds bear to storms in the United States; and the wind hauls around during the passage of the storm to the west, south-west, and south-east, and at the latter point it clears off. Mr. Edwards in his History of Jamaica says--and as a resident, his authority should be decisive as to this Island--"_that all hurricanes begin from the north_, veer back to the W. N. W., W., and S. S. W., and when they get around to the S. E. the foul weather breaks up." Doubtless the same is true of the class of northers of which we are speaking on the Gulf of Mexico. _But with this class the barometer does not rise during the gale, and in proportion to its length and violence._ With the other class of N. W. winds--the northers of winter--it does.

The following description of two winter northers, copied from Colonel Reid's valuable work, will illustrate what has been said. _Precisely such changes from S. E. rains to N. W. winds, with blue sky and detached dark clouds--fair-weather N. W. scud--occur every autumn in October and November_, and the falling of the thermometer and rising of the barometer, after rain, and a change of the wind, are perfectly characteristic.

------------------------------------------------------------------------
1843. | Wind. |Force.|Weather.| Bar.|Ther.|
------------------------------------------------------------------------
Jan. 30.| | | | | |
A.M. 4. |S. S. W. | 2 |b. c. |29.90| 77 |Off Tampico.
Noon. |South. | 5 |b. c. r.|29.86| 76 | {Lat. 23 deg. 41' N.,
P.M. 8. |South. | 6 |b. c. r.|29.84| 76 | {Long. 94 deg. 50' W.
Jan. 31.| | | | | |
A.M. 4. |S. Easterly.| 3 |b. c. |29.90| 74 | {Between 6 and 10
| | | | | | {A.M., wind was
| | | | | | {variable.
Noon. |N. by W. | 9 |c. q. w.|29.96| 76 |Norther commenced at
| | | | | | 10 A. M.
P.M. 8. |N. N. W. | 9 |c. |30.09| 73 |Lat. 22 deg. 36' N.,
| | | | | | Long. 95 deg. 48' W.
Feb. 1. | | | | | |
A.M. 4. |N. N. W. | 7 |c. g. |30.29| 63 |Lat. 22 deg. 9' N.,
| | | | | | Long. 94 deg. 50' W.
Noon. |Westerly. | 6 |c. |30.30| 67 |
P.M. 8. |Calm. | 0 |c. |30.26| 67 |
------------------------------------------------------------------------
Feb. 14.| | | | | |
A.M. 4. |S. E. | 3 |b. c. r.|29.66| 73 |At Sacraficios.
Noon. |S. W. | 4 |b. c. |29.62| |Norther comc'd at 5.30
| | | | | | P.M.
P.M. 8. |N. W. by N. | 10 |c. q. u.|29.72| 65 |
Feb. 15.| | | | | |
A.M. 4. |N. W. by N. | 10 |c. q. u.|30.10| 61 | {Gale moderated and
| | | | | | {again freshened
| | | | | | {about 8 A.M.
Noon. |N. W. by N. | 10 |c. g. q.|30.19| 61 |
P.M. 8. |N. W. | 4 |c. g. |30.20| 65 |
Feb. 16.| | | | | |
A.M. 4. |N. W. | 3 |q. |30.18| 62 |
P.M. 8. | N. N. W. | 2 | c. g. |30.21| 66 |
------------------------------------------------------------------------

b. indicates blue sky--c. detached clouds--r. rain--v. visibility of
objects--q. squalls--w. wet dew--u. ugly threatening appearance--g.
gloomy weather.

The exact counterpart of the first norther may be observed with us every fall. On the 30th January, with a rising thermometer and falling barometer, there was rain at midday. The night following was moist--the next day, about ten A.M., the wind came out N. W., with squalls and gloomy weather, a falling thermometer, and rising barometer.

The norther of Feb. 14th differed from the other only in regard to the time of the day when it commenced; the order of events was the same. The rain fell in the night--it cleared off early in the day, and the norther followed in the afternoon. This also is frequently the case with us, as every one may observe.

This brief notice of the surface winds of our climate would be incomplete without a description of those of the thunder-gust and tornado.

The former is exceedingly simple. The showers, which are accompanied with much wind, form suddenly in hot weather, and have a considerable advance condensation (frequently with obvious lateral internal action), extending eastwardly from the line of smooth cloud from which the rain is falling, or rather where the falling rain obscures the inequalities of the cloud. _The gust is never felt until the advancing condensation has passed over us_, when it takes the place of the gentle easterly breeze which previously set toward the shower. _The gust ceases as soon as the cloud has passed._ It is obviously the result of the inducing and attracting influence of the cloud upon the atmosphere near the surface of the earth as it passes over it. Let the reader watch attentively this advance condensation, from its eastern edge to the line of smooth cloud and falling rain, and he will understand at a glance this internal action of gust-clouds. The whole phenomena are simple and intelligible. A cloud approaching from a westerly point, dark and irregular from its eastern edge to the line of falling rain, where it appears smooth and of a light color; wind from the east blowing gently toward it, till the condensation is over us; then the gust following the cloud; then the rain, and in a few minutes the cloud, and wind, and rain have passed on to the east, and "sunshine" returns.

The tornado, as it is termed when it occurs upon land, "spout," if on the water, is sometimes of a different character, and as it undoubtedly had great influence in inducing the gyrating theory of Mr. Redfield, and the aspiratory theory of Mr. Espy, and has been cited by both in support of their respective theories, it deserves a more particular notice. There are several marked peculiarities attending it which determine its character.

1st. It occurs during a _peculiarly sultry and electric_ state of the trade and surface atmosphere, and at a time when thunder showers are prevailing in and around the locality, and at every period of the year when such a state of the atmosphere exists. One recently occurred in Brandon, Ohio, in midwinter.

2d. There is always a cloud above, but very near the earth, between which and the earth the tornado forms and rages. It is usually described as a black cloud, ranging about 1000 feet or less above the earth, often with a whitish shaped cone projecting from it, and forming a connection with the earth; at intervals rising and breaking the connection, and again descending and renewing it with devastating energy. Its width at the surface varies from forty to one hundred and eighty rods--the most usual width being from sixty to ninety rods. Sometimes when still wider, they have more the character of thunder-gusts, and are brightly luminous.

3d. Two motions are usually visible, one ascending one near the earth and in the middle, and a gyratory one around the other. The latter is rarely felt, or its effects observed, near the earth. Occasionally, and at intervals, objects are thrown obliquely backward by it.

4th. It is composed, at the surface of the earth, of _two lateral currents_, a northerly and southerly one, varying in direction, but normally at right angles in most cases, although not always, with its course of progression, extending from the extreme limits of its track to the axis; which currents are most distinctly defined toward the center, and upward. These currents prostrate trees, or elevate and remove every thing in their way which is detached and movable. There does not seem to be any current in advance of these lateral ones tending toward the tornado, save in rare and excepted cases, and then owing to the make of the ground or the irregular action of the currents; nor any following, except that made by the curving of the lateral currents toward the center of the spout as it moves on, and perhaps a tendency of the air to follow and supply the place of that which has been carried upward and forward, like that of water following the stern of a vessel. The south current is always the strongest, and often a little in advance of the other, and covers the greatest area. The proportion of the two currents to each other is much the same that the S. E. trades bear to the N. E. This excess in volume and strength of the southerly current will explain the irregularities in most cases, and the fact that objects are so often _taken up and carried from the south to the north side_, and so rarely from the north and carried south of the axis. These irregularities are such as attend all violent forces, and something can be found which will favor almost any theory; but the two lateral currents appear always to be the principal actors, except, perhaps, when it widens out and assumes more the character of a straightforward gust. See a collection by Professor Loomis, American Journal of Science, vol. xliii. p. 278.

The following diagram is a section of the New Haven tornado, from Professor Olmstead's map accompanying his article in the "American Journal of Science and Art," vol. 37. p. 340.

The manner in which the main currents flow is shown by their early and unresisted effect in a cornfield, as represented by the dotted lines. The direction in which the fragments of buildings were carried by the greater power of the southerly currents is shown also. And so is this irregular action, where a part of the southerly current broke through the northerly one, and prostrated two or three trees backward on the north side of the axis.

5th. This cloud, and its spout, move generally with the course of the counter-trade in the locality--_i. e._, from some point between S. W. and W., to the eastward, but occasionally a little south of east, deflected by the magnetic wave beneath the belt of showers.

6th. Several exceedingly instructive particulars have been observed and recorded.

_a_. _No wind is felt outside of the track_, as those assert who have stood very near it, and its effects show.

_b_. The track is often as distinctly marked, where it passed through a wood, as if the grubbers had been there with their axes to open a path for a rail-road. The branches of the trees, projecting within its limits, are found twisted and broken off, or stripped of their leaves, while not a leaf is disturbed at the distance of a foot or two on the opposite side of the tree, and outside of the track.

_c_. As the spout passes over water, the latter seems to _boil up_ and _rise to meet it_, and _flow up_ its trunk in a _continued stream_.

_d_. As it passes over the land, and over buildings, fences, and other movable things, they appear to _shoot up_, instantaneously, as it were, into the air, and into fragments. If buildings are not destroyed or removed, the doors may be burst open _on the leeward side_, and gable ends _snatched out_, and roofs taken off on the _same side_, while that portion of the building which is to the windward remains unaffected.

_e_. Articles of clothing, and other light articles, have been carried out of buildings through open doors, or chimneys, or holes made in the roofs, and to a great distance, without _any opening_ being made for the air to _blow_ in.

_f_. If there be a discharge of electricity up the spout from the earth, like that of lightning, the intense action ceases for a time or entirely.

_g_. Vegetation in the track is often scorched and killed, and so of the leaves on one side of a tree, which is within the track, while those on the other side, and without the track remain unaffected. (Espy's Philosophy of Storms, 359, cited from Peltier.)

_h_. The active agent whatever it is, has been known to _seize hold of a chain attached to a plow_ and _draw the plow about, turning the stiff sod for a considerable distance_. (See Loomis on the tornado at Stow, Ohio, American Journal of Science, vol. xxxiii. p. 368.)

_i_. In passing over ponds, the spout has taken up all the water and fish, and scattered them in every direction, and to a great distance.

_j_. The barometer falls very little during the passage of the spout. (See the Natchez hurricane of 1827, Espy page 337.) Not more than it _frequently_ does during gentle showers.

_k_. Persons have been taken up, carried some distance, and if not projected against some object in the way, or some object against them, have usually been _set down gently and uninjured_.

_l_. Buildings which stood upon posts, with a free passage for the air under them, although in the path of the tornado, escaped undisturbed. (Olmstead's account of the New Haven tornado, American Journal of Science, vol. xxxvii. p 340.)

_m_. A chisel taken from a chest of tools, and stuck fast in the wall of the house. (Ibid.)

_n_. Fowls have had all their feathers stripped from them in an instant and run about naked but uninjured.[5]

_o_. Articles of furniture, etc., have been found torn in pieces by antagonistic forces.

_p_. Frames taken from looking-glasses without breaking the glass. Nails drawn from the roofs of houses without disturbing the tiles.

_q_. Hinges taken from doors--_mud taken from the bed of a stream_ (the water being first removed), and let down on a house covering it completely--a farmer taken up from his wagon and carried thirty rods, his horses carried an equal distance in another direction, _the harness stripped from them_, and the wagon carried off also, _one wheel not found at all_. (American Journal of Science, vol. xxxvii. p. 93.)

Pieces of timber, boards, and clapboard, driven into the side of a hill, _as no force of powder could drive them, etc., etc._

Now to my mind, these circumstances indicate clearly, that it is not wind, _i. e._, mere currents of air, which produces the effect, but that a _continuous current_ or _stream of electricity_ from the earth to the cloud exists, and carries with it from near the earth, such articles as are movable: That this stream collects from the _northerly_ and _southerly_ side upon the _magnetic meridian_, in _two currents_ with _polarity_, which meet in their passage up at the center; curving toward the center in the posterior part as the spout moves on, when acting in a normal manner, and making the "_law of curvature_" observed: That no conceivable movement of the air alone in such limited spaces could produce such effects; or if so, that no agent but electricity could so move the air: That the air in a building could not shoot the roof upward, and into fragments; much less could the air in a cellar by any conceivable force, be made to elevate _or shoot up_ the entire house, and its inmates, and contents--effects so totally unlike what takes place in gales, hurricanes, and typhoons: That elastic free air never did nor could take hold of the plow chain, and plow up the ground; or scorch and kill the vegetation; or twist the _limbs_ from one side of a tree, while the most delicate leaves on the other, and within two or three feet, remained unaffected and undisturbed; or pick the chickens: That even if the expansion of the air could produce these effects--if a sudden vacuum were produced--_nothing but currents of electricity could produce the sudden vacuum_, by removing the air above.

It is well settled that atmospheric electricity can and does flow in currents with light, by experiments in relation to the brush discharge, etc. That it may do so without light or disruptive discharge, and in a stream, or as it is termed, by convection, with the force and effect seen in the tornado, is perfectly consistent with what we know of it--and it is, I think clearly evinced that such is the character of the phenomena, by the fact that a sudden powerful _disruptive_ discharge, _with light, up the spout_, produces an instantaneous partial or total suspension of its action; to be renewed as the cloud passes over _another_ and more highly charged _portion_ of the _earth's surface_. Peltier gives instances where the spout has been entirely and instantaneously destroyed by such a sudden and powerful discharge of electricity; marking the spot where it was so destroyed by a large hole in the earth, from which the discharge issued. And in fact these tornados are often steadily luminous, and so much so, when they occur in the night, as to enable persons to read without difficulty.

The lateral inward and upward currents, are accompanied, after they meet and unite, or seem to unite, by gyratory or circular ones. How are they produced? This question can only be answered by analogy. No permanent impressions are left by the circular currents, except to a limited extent, and in occasional instances; and observation of them has been, and must necessarily be limited and uncertain. I have witnessed one or two on a moderate scale; but owing to the suddenness of their passage, and the confusion of the objects taken up, it was difficult to determine what the circular currents were. When the southerly current is much the strongest, it appears sometimes to cross the axis, and curve round the northerly one. Perhaps this may be all the curving that really takes place, except at the posterior part of the axis, for evidence of a curving on the south of the axis is rarely, if ever seen.

Assuming, however, that the main currents unite and form one from the earth to the cloud, _induced_ circular currents would be in perfect keeping with the known laws of electricity. Such currents, and with magnetic properties, are always induced by powerful currents of voltaic electricity passing through wires. And doubtless _in all cases_ powerful currents of electricity _induce attendant circular currents_. This may account for the external gyration of the spout.

Or it may be that the two lateral currents of air which attend the currents of electricity, do not unite; having opposite polarity, but pass by and around each other, in connection with the circular magnetic currents. Future observation and perhaps experimental research will determine this. But it may not be accomplished by the present generation; for the belief that tornados are mere whirlwinds, produced by the action of the sun in heating the land, is adhered to, notwithstanding they cross the intense magnetic area of Ohio in mid-winter, and seems to be ineradicable.

The proportions of different winds vary in different localities. For the benefit of those who are curious, I copy a table from an able compilation by Professor Coffin, published by the Smithsonian Institute, showing the proportion of the winds at New Haven (the station nearest to me). It will be noticed that during the year the N. W. winds blow the greatest number of days; the S. W. next; the N. E. and S. E. less than either, and about equal. It may be observed that the two latter bear about the same proportion to the whole, that our number of cloudy and stormy days, averaging about ninety, bear to the whole number of days in the year.

+------------------------------------------------+
|Course.| 1804. | 1811. | 1812. | 1813. | Total. |
|------------------------------------------------|
| N. | 143 | 105 | 90 | 111 | 449 |
| N. E. | 99 | 207 | 138 | 138 | 582 |
| E. | 33 | 18 | 22 | 23 | 96 |
| S. E. | 131 | 108 | 135 | 110 | 484 |
| S. | 58 | 69 | 113 | 80 | 320 |
| S. W. | 224 | 255 | 153 | 261 | 893 |
| W. | 81 | 69 | 102 | 57 | 309 |
| N. W. | 329 | 264 | 345 | 315 | 1253 |
+------------------------------------------------+

This work of Mr. Coffin has been brought to my notice since the foregoing pages were written. The facts embodied in it will be found to comport with what I have observed and stated. In relation to the proportionate number of days in the year during which the wind blows from the different points of the compass at the several stations it is very full and able.

But it has cardinal defects. It does not show the _main currents_ of the atmosphere. It treats the surface-winds, which are incidental, as principals. The direction of the main currents is indeed shown frequently by the mean course of the surface winds, but not uniformly or intelligibly. Nor does it distinguish between the fair weather and storm winds; nor always between the trade winds during their northern transit, and the variable winds north of the trade-wind region. Hence, the deductions derived from it disclose no general system, and sustain no theory, although many very important facts appear. Some of these, Professor Coffin found it difficult to reconcile with received theories, or satisfactorily explain. For instance, he found the prevailing winds of the United States, in Louisiana and Texas, S. and S. E.; in western Arkansas, and Missouri, southerly, and in Iowa and Wisconsin, S. W., forming a curve, and evidently connected together.

Thus, alluding to the winds west of the Mississippi, and between the parallels of 36 deg. and 60 deg., he says:

"On the American continent, west of the Mississippi, there appears to
be more diversity in the mean direction of the wind, yet here it is
westerly at sixteen stations out of twenty, from which observations
have been obtained. The most peculiar feature in this region, is the
_line_ of southerly winds on the western borders of Arkansas and
Missouri. It seems to form a connecting link between the winds of
this zone and the south-easterly ones that we find south of it; and,
in some degree, to favor an idea that has been advanced, that there
is a vast eddy, extending from the western shore of the Gulf of
Mexico, to the eastern shore of the Atlantic; that the easterly
trade-winds of the Atlantic Ocean, when they strike the American
continent, veer northwardly, and then N. E., and thus recross the
Atlantic, and follow down the coast of Portugal and Africa, till they
complete the circuit."

This mean prevalence of the curving winds indicates the course of the western portion of the concentrated counter-trade, of which we have so fully spoken, and to which that portion owes its rains and fertility. Doubtless the curve would have been traced somewhat further west, if observations had been obtained from more westerly stations.

The idea of an eddy, to which Professor Coffin alludes, is of course unsound; that of a counter-trade, most fully confirmed; the curve corresponding with that of the regular rains and fertility as they are known to exist.

Professor Coffin is a believer in the generally-received theory of rarefaction, as the cause of all winds. His work is published by the Smithsonian Institution, and the theory is, so far forth, nationalized. But he found it very difficult to reconcile all the facts he obtained, with the theory, and, possessing a truth-loving mind, he frankly admits it. Alluding to the prevalence of N. E. winds off the coast of Africa in the summer months, as shown by certain numbered wind-roses, he says:

"Nos. 81, 83, 86, and 91, have caused me much perplexity. The arrows
for the warmer months evidently indicate a point of rarefaction
situated to the _south_ or _south-west_, and yet all the observations
from which they were computed were taken within a few hundred miles
of the African coast and desert of Sahara; a region, the annual range
of whose temperature must be exceedingly great. The only way in which
I can account for a fact so astonishing, is, by supposing the
deflecting forces at these numbers to be secondary to the influence
which we see so strongly marked in Nos. 88, 89, and 90. Let us, then,
first devote our attention to these."

(We have not space for the map of Professor Coffin, nor is it necessary to insert it. The numbers 81, 83, 86, and 91, refer to respective portions of the Atlantic, west of Africa, North of the Cape de Verdes, of 5 deg. of latitude each, where the N. E. trades are drawing off from the coast. The Nos. 88, 89, and 90 refer to like portions _below_ the Cape de Verde, where the S. W. monsoons are found under the rainy belt; and the explanation of the distinguished author is an attempt to account for the blowing of the trades _from_ Sahara, by supposing them connected with the monsoons further south, which seem to blow toward it.)

"The intense heat of the Great Desert rarefies the air exceedingly
from June to October, inclusive, and hence the arrows of unparalleled
length (Plate XII.)," (showing the monsoon winds below the Cape de
Verdes,) "pointing toward it during those months, the longest being
longer than that which represents the most uniform of the
trade-winds, in the ratio of 104 to 89. The influence of this
rarefaction is sufficient to curve the powerful current of the
trade-winds in the manner exhibited on Plate VII. Nos. 89 and 90, and
to produce the not less remarkable change in No. 88, holding the
current back and retarding it, so that its progressive motion in the
_three_ months of July, August, and September united, hardly exceeds
that during any _one_ of the colder months of the year. But while
this is so, the trades on the western side of the Atlantic are
pursuing nearly their regular track, being but slightly affected by
these influences. As a consequence, the latter must leave, as it
were, a partial vacuum behind them, which is filled by air flowing in
from the north-east and south-east. This will account for the seeming
anomaly of having a somewhat strong deflecting force directed toward
mid-ocean, in the hottest part of the year, as in the numbers above
referred to. _And yet it may be very naturally asked, Why does not
the air from these parts supply the Great Desert directly, instead of
taking a circuitous route to supply the region that supplies it? A
question which, I confess, it seems difficult to answer._"

(The italicization in the foregoing extract is mine).

Here the worthy professor finds a fact inconsistent with the theory of rarefaction--viz.: that the winds blow off shore, and toward mid-ocean, opposite Sahara, and he is "perplexed and astonished." The theory, however, must be maintained, and one of those modifying hypotheses which have made meteorology such a complicated piece of patch-work, must be invented; some "deflecting forces" found. There is the Great Desert, bordering upon the ocean, north of the Cape de Verde Islands, for a distance of six hundred miles, widening as it extends inland, whose temperature, as he says, "_must be exceedingly great_;" and doubtless is so, and yet the air, instead of blowing in upon it in a hurricane, is actually drawing off from it, and blowing towards the S. W., where the water and air do not rise above 84 deg.. Well may he be "perplexed and astonished."

Turning south, however, to the distance of five hundred miles or more, he finds the S. W. monsoon winds, which in those months blow under the belt of rains, toward the land, in the direction of, but at a great distance from, Sahara. It is an easy matter to suppose that they reach the Great Desert and supply its vortex of rarefaction, inasmuch as they blow in a direction toward it, and distance is no impediment to supposition.

Then it is necessary to _suppose_ that the S. E. and N. E. trades, at the south-west, draw so strongly to the westward as to create a partial vacuum to the S. W. of Sahara, which is filled by the winds which draw off shore, and then we have the supply brought from the distance of five hundred miles or more, by an ascending vortex, which creates a vacuum, and the air near the vortex taken away in _another_ direction by a _partial_ vacuum; and so an ascending _vortex_, which creates a vacuum is supplied from a distance, and a _partial vacuum_ at a distance is supplied by the air near the perfect vacuum. Such an idea of a supply by a circuitous route, and secondary influence, is not very philosophical, to say the least, and Professor Coffin feels it; and to the question, Why is it so? which, he says, may very naturally be asked, he confesses there is no answer. And there would be none, even if his suppositions were based upon facts. But other questions might be asked equally difficult to be answered, viz.:

1st. Is there any rarefaction which can draw the trades to the west, and in that particular locality, in opposition to the supposed vortex of Sahara, by creating a _partial vacuum_?

2d. Are they in fact so drawn?

3d. Do the S. W. winds, south of the Cape de Verdes, and _under the rainy belt_, which in the summer months extend up to these islands, _reach the desert at all_?