Chapter XI (2)

When the condensation is obvious, but thin, at nightfall, it may not, as I have said, be discernible in the evening. But there are methods by which the incipient storm condensation may be detected. The number of the stars visible, and the _distinctness_ with which they may be seen, indicate the absence or presence of condensation and its density. Virgil, alluding to the indications of fair weather, says:

"_Brightly_ the stars shine forth; Cynthia no more
_Glimmers_ obnoxious to her brother's rays;
Nor fleecy clouds float lightly through the sky."

The brightness of the stars and the clear appearance of the moon show the absence of condensation and the _dissolution_ of the fleecy clouds at the close of the day is, as we have seen, always a fair-weather indication.

There is much true philosophy in the allusions of Virgil to the moon. Thus--

"When Luna first her scatter'd fires recalls,
If with _blunt horns_ she holds the _dusky_ air,
Seamen and swains predict th' abundant shower."

The horns, or angles of the moon will, of course, appear distinct and sharp or indistinct and blunt, in proportion to the amount of condensation in the atmosphere which impedes the passage of the light. For the same reason, when the moon is new, her entire disk is visible when the atmosphere is very clear, by reason, as is supposed, of light reflected from the earth to the moon and back to us. This double reflection can only take place when the atmosphere is very clear. Hence, Virgil alludes to it, and correctly, as an indication of continued fair weather:

"If (mark the ominous hour!)
The clear fourth night her lucid disk define,
That day, and all that thence successive spring,
E'en to the finished month, are calm and dry."

Probably Virgil alluded to a month of the summer trade-wind drouth which reaches up on Southern Italy. But that appearance of the moon is occasionally seen here, and the indication is, in degree, philosophically true.

It is somewhat more difficult to determine what will be the result of the condensation seen at the west in the morning, and which is not so far east, or of such a character, as to reflect the rays of the sun; for, although always suspicious, it is sometimes of a foggy character, and disappears between eight and nine o'clock. If it increases in density after ten o'clock, or is of a dense cirro-stratus character, rain may generally be expected. If of a decided _cirro-cumulus_ character, it is certain to disappear. Cirro-cumulus is seen in small patches, with small, distinct, and rounded masses, in summer, in the morning, and sometime, during the day, after high fog has disappeared, and at other times, and is always, when of that _distinct_ character, a fair weather indication. I have seen it thus when the wind was blowing from the N. E., and the scud running toward a storm passing near, but to the south of us, when those who relied upon the existence of the wind and scud as evidences that we were to have the desired rain, were deceived. Thus, the couplet from an old almanac:

"If _woolly fleeces_ strew the heavenly way,
Be sure no rain disturb the summer day."

When this morning condensation is not high fog, and is dense and passing east with a wavy appearance, it is very certain to rain. Jenner says:

"The boding shepherd heaves a sigh,
_For see, a rainbow spans the sky_."

An old almanac had the following verse:

"A rainbow in the morning
Is the shepherd's warning;
A rainbow at night
Is the shepherd's delight."

So the proverb was originally made; but as our ancestors were not shepherds, and had a horror of ocean storms, it was commonly quoted, in this country, in the following form:

"A rainbow in the morning,
The sailors take warning," etc.

Rainbows are not reflected from _clouds_, but falling rain, and a morning rainbow at the west is, of course, evidence that it is _actually raining there_, and will, in all probability, pass over us. "Thunder in the morning, rain before night," is a common saying, and a true one. There is a belt of showers, or showery period approaching, of unusual intensity--for thunder showers in the morning are rare. The afternoon is their most common period, and they are very apt to appear then, when the morning is showery.

Of the different forms of cirrus and cirro-stratus, which appear during the day, and indicate approaching storms, or of cumulus indicative of showers, it is difficult to give an intelligible description without very many illustrations. I have many daguerreotype views, taken at different seasons of the year, and at a time when different forms of cirrus and cirro-stratus condensation, indicative of storms, exhibited themselves. They differ, as I have said, and it must be remembered, very much at _different seasons_ of the year, and in _different years_, and their delicate shades are taken with difficulty by the artist, and reproduced with difficulty, and only at considerable expense, by the engraver; and I have omitted them. The time will come when a knowledge of their language will be sought for and read--when the "countenance of the sky" will be an object of intelligent interest to all whose business may be affected by the weather, or who love to learn of nature. But it is not yet. This is the age of theory and speculation. The time of actual, practical, connected observation and prognostication, which may justify expensive illustration, is yet to arrive.

The reader will find in the general plates representations of several kinds of cirri. They are delicate, always white, more or less fibrous, and form in the upper part of the trade or the adjoining atmosphere above it. Their character and elevation should be studied, and the observer should be careful to distinguish which is the most elevated. Not unfrequently it may seem, to a hasty observer, that the cirrus is below the cirro-stratus or forming stratus. But the genuine cirrus never is. It forms near, and above, the point of congelation, and is often composed of crystals of ice or snow. If they fall, they melt and evaporate, when there is no storm, before reaching the earth. Aeronauts have met with them and their crystals when there was no fall of moisture at the surface of the earth; and the angles of reflection exhibited by halos and other optical phenomena which form in them, enable us to detect their crystallization and the form of it.

They are produced by electric changes which condense the vapor, and the coldness of the air at that elevation freezes it at the _instant of its condensation_.

Congelation is crystallization, and all crystallization is electric, or magneto-electric. The snow-flakes differ in form and size according to the suddenness of the condensation, the amount of moisture condensed, the polarity of the strata through which they pass, and their consequent attraction and adhesion to each other.

The connection of electricity with these formations of cirri has frequently been admitted, and it is perfectly obvious that the long fibrous bands, shooting from horizon to horizon, could not be formed by commingling of currents any more than the perfectly isolated, distinct, enlarging-outward cumulus hail-storm, could be so formed. Cirri form at the line of meeting, between the trade and the upper atmosphere, and in one or the other, or both, very much according to the season, and the suddenness with which storms are produced. These often _induce_ a layer of cirro-stratus or stratus at the lower line of the counter-trade, and in the surface-atmosphere, which precipitates; and this operation is clearly discernible, and very frequently, before gentle rains. Condensation in the whole body of the trade is usually in the form of turbidness or mistiness, a bank or incipient stratus, without cirri.

It seems matter of astonishment that water should float so far condensed, in strata where the air is so much lighter, without being precipitated. But electric attraction and repulsion between the different strata and the vesicles, explain it.

In mid-winter, the cirrus forms are prevalent and most distinct. After severe cold weather, when a storm approaches, the cirri form in long, narrow threads, parallel to each other, extending from about W. S. W. to E. N. E., gradually thickening and forming, or inducing, cirro-stratus and stratus, and dropping snow. This form is called the _linear_-cirrus. The tufted, and other fibrous forms, are seen in patches also, in great distinctness, during these mid-winter days, when the wind gets around to the southward, and the weather is pleasant. Such days are called "_weather-breeders_," and their _offspring_ the patches of cirrus, which are to extend and compose, or induce the storm, and indeed are an advance part of it, are then never absent. A clear, moderate day, in a normal winter, with wind from any southern point, however light, between the 1st of January and the middle of February, without these patches of cirrus, is very uncommon. Watch and see whether they tend to cirro-stratus, or whether the wind gets around to the N. W. at nightfall, and they disappear. If the former, a storm may be expected; if the latter, fair weather.

Thus there are three peculiarities attending the forming cirrus of mid-winter (1st of January to 10th of February): long, fibrous, parallel bands in the morning (linear cirrus), gradually coalescing as the day advances, after severe cold; the comoid, curled, or tufted cirrus, in curling bunches, called "_mares'-tails_," and the _transverse_, when the fibers are in bands or threads, which are not parallel, but cross each other at angles, more or less acute. The two former varieties are represented on Figure 5, page 26, indicated by one bird, but the last form is a very prevalent one in our atmosphere.

Various names have been given to different forms of _cirro-stratus_. Those represented in Figure 5, page 26, are the "_cymoid_" on the right, the "_mottled_" on the left, below the cirro-cumulus; and the "_linear_" below that. The form known as the "_mackerel sky_" is not represented there. It consists of regular forms, resembling the _waves_ on the surface of the water when the wind blows a gentle breeze. But the _wavy_ form, and of all sizes, is very frequently assumed by cirro-stratus, which is rapidly condensing, and turning to stratus. In the "mackerel sky," strictly so called, the waves are small, parallel, nearly distinct and equi-distant, and resembling the appearance of a school of mackerel, swimming in the same direction, one above another. All _wavy_ forms of cirro-stratus indicate a disposition to increased condensation and rain. When the waves are very large and dense, and cross obliquely, or unite at one end, rain is very certain to fall soon, if the line of progress of the condensation is over the observer, and the clouds are seen in the western or N. W. quarter of the sky.

But there are few forms which are not occasionally seen when no rain or snow falls. The intensity of the electric action which produces them may not be sufficient to effect precipitation, or they may be the attendant, attenuated _lateral_ condensation, which frequently "thins out" a considerable distance from the dense, precipitating portions of the storm.

If that denser portion is north of us, the probabilities of rain are greater, for there is always a probability that the storm may be of the character which is extended south, by a polar wave. The observer must watch the formation of cirri, and the different forms of cirro-stratus and stratus, and become familiar with their appearance. It is not a difficult task. With the aid of a few general directions he will soon be familiar with them:

1. Get a correct idea of the different characters of the primary clouds. The true fibrous _cirrus_--the different forms of _cirro-stratus_--the smooth, uniform _stratus_--the _cirro-cumulus_, which is nothing but a cirro-stratus, separated into _distinct masses_ by the repulsion of static electricity--and the _cumulus_, too distinct ever to be mistaken. There is no difficulty, except with the varied forms of cirro-stratus. It is useless to attempt to give, or the observer to rely on, names for these numerous forms, without as numerous illustrations. Those in use are rarely applied correctly. I have never met with ten persons who applied even the term "mackerel sky" to the same precise form of cirro-stratus. In relation to all of them it is to be observed that polar belts of condensation, and local appearances of considerable extent, are often too feeble in action to precipitate, even when the mackerel form is present; and all may be the lateral attendants of passing storms. Therefore,

2. Satisfy yourself whether the cirrus or cirro-stratus increases in density and tends to the formation, or induction, of stratus; and whether it is isolated, or an extension of the condensation of a storm, and if the latter, _where that storm is_. The time will come when an intelligent use of the telegraph will do this for you.

3. Look also to the character of the wind, if there be any. On this subject I have perhaps said all that is necessary in the preceding pages. Next to condensation, the direction and character of the wind is the most valuable prognostic. Indeed it often tells us that a storm is approaching, and the quarter from which it will come, and its character, before the condensation is visible.

4. See if there is any _secondary_ condensation or scud. These are sometimes seen running toward a storm, when there are not distinct clouds visible in the western horizon, at nightfall, or in the evening, as in the instance stated in the introduction, and sometimes from the north-east, as in cases heretofore so often stated. But the easterly scud do not often form in winter, until after the cirrus has passed into the form of cirro-stratus, or has induced the latter forms in the inferior portion of the trade, or the surface atmosphere.

The inductive effect of the primary condensation, therefore, is not always, and especially in winter, sufficient to create the easterly current and scud, and it is often the case that the easterly wind is not felt, or the scud seen, in snow-storms, until the snow has begun to fall, and the first snow will fall with a S. W. air, as I have heretofore stated. But when the condensation has so far advanced toward stratus that the easterly wind and scud are obvious, there is little or no doubt that rain or snow will fall speedily. The occasional occurrence of easterly wind and scud, without rain, however--dry north-easters, as I have termed them--in connection with storms passing south of us, or condensation too feeble to precipitate, should be remembered. The long, dry, north-easterly winds of spring have been attributed to the icebergs, but they are overlaid by feeble stratus or cirro-stratus condensation, or are the result of attraction, by a more southern precipitation. The observer must be careful to distinguish between the various forms of N. W. scud and cirro-stratus, which they sometimes resemble. This he may do _from the direction in which they move_. Cirro-stratus always moves from some point between S. S. W. and W. S. W. to some point between N. N. E. and E. N. E. The various forms of N. W. scud move to the S. E. The March, foggy scud, from between W. and N. W., rarely have any cirro-stratus above them, but rather a peculiar turbid condensation.

The character of the primary condensation, the direction and force of the wind, and the direction of the secondary condensation or scud, must be the main reliance of the observer. But I must reiterate that they all differ in different kinds of storms, in different seasons of the same year, and the same seasons of different years; and the observer must be careful to make due allowance for those differences.

There are, however, divers other secondary signs, which, although not alone to be relied upon, will aid the observer, if carefully studied, when the character of the clouds, and the pressure of easterly or southerly wind and scud, are not decisive. Of these, a large class are electrical.

The smoke descends the adjoining chimney-flues, or outside of the chimney, toward the ground.

Thus, Darwin, as quoted by Hone:

"The smoke from chimneys right ascends,
Then, _spreading_, back to earth it bends."

Smoke is electrified _positively_, by the act of combustion; the earth and the adjacent atmosphere, when storms are gathering or approaching, is _negative_. Hence the smoke spreads, and is attracted downward by an opposite electricity. On the other hand, it is interesting to see, at other times, and when the difference in temperature is not material, but the whole atmosphere is positive, with what rapidity and compactness the smoke will ascend in a _straight and elevated column_ from the chimney, repelled by a similar electricity. I am aware it is generally supposed the smoke descends because the _air is lighter_. But it is a mistake. I have seen it descend when the barometer was at 30 deg..60, or .60 above the mean.

There is, too, a draught downward in chimneys, in such cases when there is no smoke or fire in any of its flues. Thus Jenner says: "The soot falls down;" whether he meant by this that there was an actual fall of soot other than what is occasioned by the rain falling in through the chimney top, and disturbing the soot, as sometimes happens, I do not know. It occurs rarely, and is of very little practical importance. But every housewife knows that chimneys, which have been used in winter, and are full of soot, _smell_ before storms. The odor results from a downward draught and the dampness of the air. So the smoke from one flue will descend another, into some unused room, on such occasions. Another class of these electrical signs are felt by those who are suffering from chronic diseases, which have affected the nerves and made them sensitive. Thus Jenner:

"Old Betty's joints are on the rack."

And Hone adds:

"Her corns with shooting pains torment her,
And to her bed untimely send her."

But Old Betty's rheumatism or corns are not alone in this. Those whose bones have been broken feel it. All invalids feel it. And, indeed, all observing healthy persons may, and do, although all are not distinctly conscious of it. It is common for such to say, I feel sleepy, or I feel dull, or, It _feels_ like snow, or _feels_ like rain, and thus from their own feelings to be able to predict, not only falling weather, but its _character_, whether snow or rain, at a time when either may occur consistently with appearances.

This change is a change from the positive electricity which is so congenial to the active--"bracing" is the usual term--to negative and damp--for this change is accompanied by condensation, as I believe all changes from positive to negative are. Certain it is, if the atmosphere is highly charged with negative electricity, condensation takes place; if with positive, evaporation. Perhaps it is a change of the associated electricity which accompanies magnetism, and not of the free atmospheric electricity alone. Hence another phenomenon alluded to by Jenner:

"The walls are damp, the ditches smell."

There are localities where this dampness is very obvious. The celebrated William Cobbett, many years since, when a farmer on Long Island, observed and published the fact that the stones grew damp before a storm. I know of flagging stones that usually grow damp two or three hours before rain, especially in spring and fall, and every step taken upon them is made visible by a corresponding increase of condensation.

The reverse of this takes place just before the close of storms. Flagging stones, and walls under cover, will frequently become dry before the rain ceases. The negative electricity becomes less as the positive prevails, although the clouds above are still dropping rain.

In the comparatively moist, showery climate of England, these changes from positive to negative alternate rapidly between successive showers; but observations of electric phenomena, or of clouds, in that climate, are not, without qualification, safe guides for us.

So "the ditches smell," particularly in the evening before a rain, when the immediate surface-atmosphere is charged with negative electricity, and the _condensing moisture_ prevents the diffusion of the odors. For the same reason the candle will not relight, and there is crackling in the ashes or lamp. Thus, again, Virgil:

"Maidens that nightly toil the tangled fleece
Divine the coming tempest; in the lamp
_Crackles_ the oil, the gathering wick grows dim."

Virgil did not live in our cold climate, and knew nothing of the crackling in the fire, or in the ashes or coals which remain after the wood is consumed. The lamp exhibits it on a smaller scale, and perhaps he had noticed it when in company with the maidens. But it is sometimes noticeable even in the lamp or candle with us. A small particle of moisture will produce it, in a marked degree, at any time.

In winter, when the air is highly positive and cold, the candle can be blown out, and by another puff of the breath relighted, with ease. But when the electricity before a storm becomes negative, and partial condensation takes place, this can not be done. This partial condensation before storms and showers shows itself upon vessels containing cold-water, in summer. It seems to be the received opinion, that the condensation is evidence of a greater _quantity_ of moisture in the atmosphere. But this, too, is a mistake, and hence the little reliance to be placed on hygrometers.

This partial condensation is sometimes visible. When the sun shines clearly, at the east or west, through a _small opening_ in the clouds, the condensing vapor is shown by the streaks of sunlight, just as the fine particles of dust are seen in a dark room, when a few rays of sunlight are admitted through a small aperture. This phenomenon is often observed, and it is said of it--"It's a going to rain; _the sun is drawing water_."

Virgil alludes to this as seen in the east in the morning, thus:

"But when beneath the dawn _red-fingered rays_
Through the dense band of clouds _diverging_ break,

* * * * *

Ill does the leaf defend the mellowing grape;
Leaps on the noisy roof the plenteous hail,
Fearfully crackling."

It is well ascertained that storm-clouds of great intensity have polarity in the different portions, and that in the less intense magneto-electrical climate of England isolated showers are often of this character--the polarity existing in rings. Showers are doubtless thus found with us. Mr. Wise got into one of them; see his description (Theory and Practice of Aeronautics page 240).

I have, in another place, alluded to the upward attraction of the dust beneath the advance condensation of a shower. Jenner alludes to it in the following lines:

"The whirling winds the _dust_ obeys,
And in the rapid eddy plays."

So Virgil:

"Light chaff and leaflets, _flitting, fill the air_,
And sportive feathers circle on the lake."

All these are electrical.

In England, where the action of such isolated clouds is less intense, the different electricities in different portions of the cloud, whose opposite and changing action produce all the phenomena, the condensation, the cold and congelation, the currents, etc., have been accurately ascertained. We can not get into the situation occupied by Mr. Wise. But every man may observe these _intestine motions_ occasionally, in the advance condensation of an isolated thunder-shower, in front of, but near the smooth line of falling rain. They are more lateral than upward or downward, and are often exceedingly rapid in movement.

I have said that hail has often been found to fall from particular and well-defined portions of a cloud, and rain from the other portions, the hail being positive, and rain negative. An instance of very striking character may be found in Espy's Philosophy of Storms (Introduction, page xx.) Doubtless in all cases thunder-showers, which are isolated and distinct, have opposite electricity in different portions, to whose active agency all the phenomena are owing. And the return of electricity to the earth in the rain explains the greater fertilizing effect of the latter compared With all artificial watering. He was a true philosopher who attempted to stimulate vegetation by electricity.

Sounds may sometimes aid the observer in doubtful cases in foretelling the weather. The roar of the surf, or breaking of the waves on the shore, when great bodies of water are disturbed by a precedent storm-wind, often heard before the wind is perceived on the land, I have already alluded to. And thus Virgil:

"When storms are brooding--in the _leeward gulf_
Dash the swelled waves; the mighty mountains pour
A harsh, dull murmur; far along the beach
Rolls the deep rushing roar."

The moaning or whistling of the wind all have noticed. It is not uncommon to hear the expression, "The wind sounds like rain." Jenner says:

"The _hollow_ winds begin to blow."

And Virgil:

"The _whispering_ grove
Betrays the gathering elemental strife."

This whispering is the motion of the leaves; and they are often stirred by a peculiar motion which is not that of wind. Sometimes every leaf upon a tree may be seen _vibrating_ with an _upward and downward_ motion, when there is not wind enough to stir a twig. This interesting phenomenon is electrical. Trees, and all vegetables, confessedly discharge electricity, and such discharges move the leaves, when very active.

With us, sounds can be heard more distinctly from the east or south, before storms, according to the character of the coming wind. Howard mentions an instance when he heard carriages five miles off. Steamboat paddles, rail-road cars, and other sounds, are often heard a great distance. The distance at which the now common steam-whistle is heard, and the direction, is not an unimportant auxiliary indication of the weather. Howard attributes these peculiar phenomena to the "_sounding board_," made by the _stratum of cloud_; but sounds may be heard from the north-west, when there is no condensation, and the wind is from that quarter, and also from the east when it is not cloudy; and in a level country the village bells often tell the direction of the current of air just over our heads when we do not feel it at the surface. The wind is undoubtedly moving in a rapid, and perhaps invisible current, not far above us. If from the east or south, it betokens rain; if from the western quarter, fair weather.

The conduct of the different animals furnish a considerable portion of the signs alluded to by Virgil and Jenner, and are never unimportant auxiliary evidence of the approaching changes, whether from dry to wet, or wet to dry.

The observer will find, in the conduct of our birds and animals, especially those which are not domestic, ample evidence of the truth of the descriptions of Virgil. He denies the animals and birds foresight, but he does not seem to have observed that the swallow leaves for the south as soon as the _autumnal_ change begins to be felt, and in August; nor the evident sagacity of other _migratory_ birds. They do not act from the "_varying impulse_" produced by an actual state of things, but a knowledge or apprehension of those which are to come. This is nothing more or less than foresight. So foresight tends to prudence and skill, and they exercise both, and with reference to the future. The goldfinch does not build her nest in the hole of the tree, or in the crotch of the limb; but _hangs it_ with _exquisite skill_ on the slender _waving, outward branch_, where no animal, or larger bird, or any depredator, can be sustained. She is not more timid than others; why does she invariably thus build? What makes her "_impulses_" differ from those of other birds, and always in the _same manner_?

Jenner, too, has grouped, in admirably descriptive language, many of the peculiarities exhibited by animals and birds before approaching storms, some of which exhibit foresight, and others not.

Perhaps the rooster, who keeps ceaseless watch over his harem, is the most reliable weather-watcher we have. In my earlier days, when it was the practice to keep valuable birds of the kind much longer than it now is, and they had opportunity to become _experienced_, it was interesting to observe how closely they watched the weather. I well remember a venerable chanticleer, who, perched on the tree among his hens, would always foretell the coming storm of the morrow, by sounding forth _in the evening_, and _often_, his defiant note. Such note in the evening was invariable evidence of foul weather. And during the night, their earlier and more frequent crowing is often indicative of it. It is, however, in the earlier part of the day, in doubtful cases, that no inconsiderable reliance may be placed on their sagacity. Often, when a storm is gathering in the forenoon, they will announce it by an almost incessant crowing. The habits of an _experienced_, old-fashioned bird, of this kind, will well repay attention; but I can not answer for the Shanghai and other _fancy breeds_.

Jenner says:

"The leech disturbed, is newly risen
Quite to the summit of his prison."

Few have had, or will have, opportunities to observe this, but it is strikingly true. It is difficult to conceive how mere condensation, from an increase of vapor in the atmosphere, should be foreseen by the leech in his watery prison. It is obvious, I think, there is an electric change which reaches him, as it does the whole animal creation, the once broken bones, and the joints of Aunt Betty. Thus much of the philosophy of signs.

_The barometer_ is a useful instrument, in connection with observations of the other phenomena. It is especially useful to the sailor, as its indications relative to the winds are much the most certain. But it is not, _alone_, to be relied upon. This is well settled, although the reasons for it have not been understood. Why it should rise sometimes before storms, in opposition to the general rule--or fall at others without rain--or rise occasionally during the heaviest gales, has been a mystery, and impaired the confidence in its accuracy and usefulness even of the class of philosophers of whom Sir George Harvey spoke, in the sentence quoted in the introduction. But, as I have already intimated, it is all very intelligible.

I have said that the barometer has no fair weather standard--the mean of 30 inches at the level of the sea being an _average_ of the _fair weather_ elevations and the _foul weather_ depressions. Its fair weather position, it would seem, must be above the mean, therefore, and as much above as its foul weather depressions are below. But this is not precisely true. Its extreme fair weather range is 31 inches, and it rarely reaches that; while its lowest storm range is down to 28, and is the most often reached of the two. My barometer stands about 40 feet above ordinary high-water mark. It is not a "wheel," but an open, "scale" barometer, and a perfectly good one. Its most reliable fair weather standard is about 30-30/100 inches. It is its _most common summer, set fair position_, but that position is often at other and different elevations, at other periods of the year, during fair weather. The reader must observe for his own locality, and satisfy himself what the most common set fair position for the barometer is, at the different periods of the year, where he resides. When he has ascertained this, he may apply the following principles to illustrate its exceptional action, and in judging of the future of the weather:

1st. _As to its rise before storms._--Supposing it to have been stationary, at or about a set fair position, _for the period_, and for one or two or more days, a very _gradual_ and _moderate_ rise is an indication of continued fair weather; and a _sudden_ and _considerable rise_ is indicative of a storm. If the sudden and considerable rise occurs in the latter part of spring, summer, or early autumn, it indicates a storm of the _first_ or _third classes_ described in Chapter X., if in winter, a storm of the _first class_ only. If the elevation is _very_ sudden and considerable, the storm will probably be _severe_. The philosophy of this, according to my present apprehension of it, is, that these storms present an _extended easterly front_--_settle very near the earth_--and _have a rapid progress_--thus accumulating the atmosphere somewhat, in advance of them.

2d. _As to its fall before storms without previous rise._--This is always very regular before the second class of storms, or polar belts of showers and storms. It is very fairly exemplified in the table from Reid, on page 329. The barometer, so far as I have opportunity to observe, does not rise from a stationary position on the approach of this class of storms. At the commencement of heated, summer, dry terms, my barometer has most frequently ranged at about 30.30, and gradually, but slowly, fallen below 30 inches before the belt of showers arrived, and the term closed. The fourth rule of Dalton (Meteorology, page 183) indicates a similar law in England. It is as follows:

"In summer, after a long continuance of fair weather, with the
barometer high, it generally falls gradually, and for one, two, or
more days, before there is much appearance of rain. If the fall be
sudden and great for the season, it will probably be followed by
thunder."

3d. _It falls frequently and considerably without rain._--This is owing to the fact that _all_ regular, periodic efforts at condensation do not result in rain. The second, third, and fourth classes of storms described, may not (as we have said) _be sufficiently active to precipitate_, although the _series of phenomena_ (including the fall of the barometer) may be, in other respects, perfect. Such an instance may be found in Reid's table, on page 329, and on the 11th of the month. But the fall in such cases is not as great, unless the wind be violent.

4th. _It rises during considerable gales._--But these are of the kind so often alluded to--viz., the N. W., in the northern hemisphere, and the S. W., in the southern; and the _philosophy_ of it has been explained, and is observable.

With these explanations, the reader will be able to understand, and practically apply, the barometric changes, in connection with the other phenomena, in forming an opinion of the weather.

_The thermometer_ is also an auxiliary. It _rises_, during the winter half of the year, in the _advance portion of the storm_, and falls when it passes off again; and the reverse is true, as we have seen, when its range is very high in summer. It is, therefore, to some extent, a useful auxiliary, although of minor importance.

_The hygrometer_ is of less importance still. It is not in general use as a practical guide to the changes of the weather, and does not deserve to be.

A question, which has been much mooted, deserves a passing notice in this connection--viz., whether our climate has gradually become ameliorated and milder on the eastern part of our continent, since its settlement. I have not space left for its discussion. Humboldt (Aspects of Nature, page 103) is of opinion that there has been no material change. He says:

"The statements so frequently advanced, although unsupported by
measurements, that since the first European settlements in New
England, Pennsylvania, and Virginia, the destruction of many forests
on both sides of the Alleghanys, has rendered the climate more
equable--making the winters milder and the summers cooler--are now
generally discredited. No series of thermometric observations worthy
of confidence extend further back, in the United States, than
seventy-eight years. We find, from the Philadelphia observations,
that from 1771 to 1824, the mean annual heat has hardly risen 2 deg..7
Fahrenheit--an increase that may fairly be ascribed to the extension
of the town, its greater population, and to the numerous
steam-engines. This annual increase of temperature may also be owing
to accident, for in the same period I find that there was an increase
of the mean winter temperature of 2 deg. Fahrenheit; but, with this
exception, the seasons had all become somewhat warmer. Thirty-three
years' observation, at Salem, in Massachusetts, show scarcely any
difference, the mean of each one oscillating within 1 deg. of Fahrenheit,
about the mean of the whole number; and the winters of Salem, instead
of having been rendered more mild, as conjectured, from the
eradication of the forests, have become colder, by 4 deg. Fahrenheit,
during the last thirty-three years."

The facts hereinbefore stated show that there is nothing like a _regular_ amelioration; that the seasons differ during the same decade, and different decades. The cold decade, from 1811 to 1820, has not been reproduced. But it may be, and we know not how soon. Since that period there has certainly been a change--for even the cold period from 1835 to 1840 did not equal that from 1815 to 1820, nor indeed those of 1775 to 1780 or 1795 to 1800. But as these variations, so far as we are enabled to judge, depend upon the varying influence of the sun's rays, and of volcanic action, it is impossible to say that equally cold periods will not return, during the latter half of this century.

If the influence of the sun was constant, and volcanic action regular, two causes would tend to modify the seasons:

1st. The exposure of the surface to a more effective action of the solar rays, by a removal of the forests, and by drainage. That such action would be more effective upon a surface thus uncovered and drained, can not be doubted.

2d. _The movement of the area of magnetic intensity, and the magnetic pole, to the west._--There is such a movement, and its progress can be measured by the increase of declination on the east of it, and its decrease on the west. And the effect of it on climate is unquestionable. In all probability it has had an influence upon ours; and a removal of that area and pole still further west--60 deg. or 80 deg.--would change the location of the concentrated trade, and the Gulf Stream, and restore to Greenland the fertility she once had, and which the Faroe Islands now enjoy. And, on the other hand, its removal as far east of its present position would again depopulate Greenland, and render it again inaccessible. But I can not pursue this subject.

Finally, assistance may be derived from the occasional, although imperfect, accounts of the state of the weather elsewhere, which the newspapers afford. I have been much indebted to the Associated Press of New York for intelligence contained in their telegraphic reports. Occasionally they have been very full and instructive.

On this point, however, there is less of reality in the present than of hope in the future. The time must come when the collection and dissemination of meteorological truth, will be deemed an object of national importance, and national duty. Population is increasing, by immigration and propagation, in a rapidly progressive ratio. There has been great danger that it would outrun agricultural production. A short crop this year would have been disastrous to our prosperity--and the danger was imminent. Every description of business, and every financial circle, felt that fever of anxiety it was so well calculated to induce. The importance of extended agricultural production, and the dependence of all classes upon its success, are now in a greater measure appreciated; and none can fail to see the value of a correct understanding of the weather to the agriculturist, how short-sighted soever they may be, in relation to its direct influence upon their own prosperity and happiness.

Our country is, physically, a most favored one. The facts disclosed or alluded to in this volume show that it is without a parallel on the face of the globe; and our facilities for meteorological observation, and the ascertainment and practical application of meteorological truth, are equally pre-eminent. The great extent and unbroken surface of the eastern portion of the continent; its excessive supply of magnetism and atmospheric currents, and the consequent marked character of the phenomena; the existence and prospective increase of telegraph lines over most of its surface; the homogeneous and energetic character of a population united, upon so large a surface, under one government; the freedom of that government from debt, and the excess of its revenue; the possession of a National Observatory, with a competent philosopher at its head; and a national institution, liberally endowed, and adapted to the collection and diffusion of practical and scientific intelligence, give us an opportunity and a capacity for connected observation and investigation, and an ability to profit by it, that no other nation can boast.

We have, too, a just national pride. Our exploring ships have penetrated and made discoveries in both hemispheres, and our travelers have visited successfully every clime; and thus our national interests, and obligations, and pride, demand an organization, practical and permanent, in relation to this subject, and the time will come when we shall have it.

When that time comes--when the present _limited horizon_ of each of us is _practically extended over the entire country_--and when the actual state of the weather over every part of it is known, at the same time, to the inhabitants of every other, and every where _read in the light of a correct philosophy_, prognostication will be comparatively simple and certain; and A PROGRESS will have been made, productive of an amount of pecuniary, intellectual, and social benefit to the people, which can not be overestimated. May it come before the shadows of the night of death have gathered around us, that we may have a more perfect view of that atmospheric machinery which distinguishes our planet from others, and is, with such infinite wisdom, adapted to make it a fit habitation for man!

THE END.