The Philosophy of the Weather Part 27

"Mark, with attentive eye, the rapid sun-- The varying moon that rolls its monthly round; So shalt thou count, not vainly, on the morn; _So the bland aspect of the tranquil night Will ne'er beguile thee with insidious calm_."

All early condensation and indications derived from it, must be looked for in the west. From that quarter all storms come. These indications at nightfall are of a varied character. They may consist of primary condensation in the trade, or of secondary condensation, scud running north toward a storm, the condensation of which has not yet visibly reached us, but which will extend south and pa.s.s over us. It may be a heavy bank, or consist of narrow cirrus bands. Cirro-stratus cloud banks, in the S. W., in the fall and winter, of a foggy and uniform character, are indicative of snow. The body of the storm will pa.s.s south of us, and a portion over us, the wind be north of east, and the snow will not be likely to turn to rain before it reaches the earth, by reason of a southern middle current.

Banks in the N. W. indicate rain at all seasons. The storm is north of us, working southerly, and such storms rain on the southern border--in winter even--because they have the wind on that border from south of east. It may, indeed, snow, but if so, probably in large flakes, soon turning to rain. There are other appearances at nightfall which deserve consideration. A red sun, with smoky air, is indicative of continued dry weather, a frequent appearance in dry terms, lasting three or four days, at least, from the commencement. So is a red appearance of the sky, when there are no clouds, indicative of a fair day following. On this subject we have an allusion to the weather, by our Saviour while on earth, which, like all such allusions found in the Bible, is of remarkable philosophical accuracy. It is found in Matthew, chapter xvi., verses 2 and 3: "He answered and said unto them, When it is evening ye say, It will be fair weather, for the sky is red. And in the morning, It will be foul weather to-day, for the sky is red and lowering. O, ye hypocrites, ye _can discern_ the face of the sky," etc.

Another allusion to the weather, though not applicable to this point, I will refer to in pa.s.sing. It is found in Luke, chapter xii., verses 54 and 55: "And he said also to the people, When ye see a cloud rise out of the west straightway ye say, There cometh a shower; and so it is. And when ye see the south wind blow, ye say, There will be heat; and it cometh to pa.s.s."

This is all very true, and might have been cited to show the universality of the phenomena. But to return.

We have an old English proverb alluding to the same phenomena, of great value and truth, viz.:

"An evening red and a morning gray Are sure signs of a fair day; Be the evening gray and the morning red, Put on your hat or you'll wet your head."

The sky is red if there be no condensation at the west to obscure the rays of the sun; if there be, it is gray, or there is a bank or cloud, and it is obscured. So if there be no condensation over, or to the east of us, in the morning, to reflect the rays of the sun, the sky is gray; if there be such condensation, the sun is reflected from it, and the sky is red. Such morning condensation is indicative of foul weather. It is, as we have said, the eastern edge of an approaching storm, on, or under which, the sun shines and illumines it. Thus, at night, it shines through a portion at the west, which is situate between the sun and us, making the sky gray: but shines on, or under, a portion in the morning, east of us, but not far enough east to obscure the horizon, and the rays of the rising sun are reflected from it. In either case the red or gray appearance results from the relative situation of the sun and the eastern edge of an approaching storm.

The following couplet of Darwin is an apt description of the morning appearance:

"In fiery red the sun doth rise, Then wades through clouds to mount the skies."

The sun is often reflected in vivid colors, from the under surface of clouds, at sunset. This is an indication of fair weather. It is evident the sun shines through a _clear atmosphere beyond the cloud_, or his rays would not reach and illume the lower surface of the cirro-stratus with such distinctness. He "_sets clear_," as is said; the clouds are pa.s.sing off, and there are none beyond. It is this appearance, in different forms, when there happen to be patches of broken, melting cirro-stratus above the horizon, which makes the beautiful sunsets that attract attention. So the sun is reflected, in beautiful colors sometimes, from the c.u.mulus clouds which have pa.s.sed over to the east. The most beautiful and variegated I have ever seen, were reflected from that imperfect c.u.mulus condensation which takes place occasionally during long drouths--doubtless resembling that which is seen over Peru, hereinbefore alluded to, as described by Stewart.

It is not, then, the presence of cloud condensation at the west, at nightfall, which alone indicates foul weather; but such condensation, whatever its form, as evinces that it is not the _dissolving_ cloud of the day, but the eastern, approaching portion of a _still denser portion beyond, through, or under which, the sun can not shine clearly, but which wholly or partially obscures it_. _Remembering this philosophy of the matter_, the observer will soon be able to detect the various forms of condensation which originate or exhibit themselves at nightfall, and whether they indicate an approaching storm or not, without a more explicit specification of them. It is an important hour for observation; "Let not the sun go down" without attention.

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 pa.s.sage 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-c.u.mulus_ character, it is certain to disappear. Cirro-c.u.mulus is seen in small patches, with small, distinct, and rounded ma.s.ses, 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 pa.s.sing 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 pa.s.sing 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, pa.s.s 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 c.u.mulus indicative of showers, it is difficult to give an intelligible description without very many ill.u.s.trations. 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 ill.u.s.tration, 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 pa.s.s, 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 c.u.mulus 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-c.u.mulus; 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 a.s.sumed 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-c.u.mulus_, which is nothing but a cirro-stratus, separated into _distinct ma.s.ses_ by the repulsion of static electricity--and the _c.u.mulus_, 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 ill.u.s.trations. 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 pa.s.sing 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 pa.s.sed 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 pa.s.sing 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.