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THE PHILOSOPHY OF THE WEATHER.
AND A GUIDE TO ITS CHANGES.
BY T. B. BUTLER.
NEW YORK:
D. APPLETON & COMPANY,
NOS. 346 & 348 BROADWAY.
1856.
Entered according to Act of Congress, in the year 1856, by
T. B. BUTLER,
In the Clerks Office of the District Court of the District of
Connecticut.
ELECTROTYPED BY
THOMAS B. SMITH,
82 & 84 Beekman Street.
PRINTED BY
J. F. TROW,
379 Broadway.
INTRODUCTION.
The atmospheric conditions and phenomena which constitute "The Weather"
are of surpassing interest. Now, we rejoice in the genial air and warm
rains of spring, which clothe the earth with verdure; in the alternating
heat and showers of summer, which insure the bountiful harvest; in the
milder, ripening sunshine of autumn; or the mantle of snow and the
invigorating air of a moderate winter's-day. Now, again, we suffer from
drenching rains and, devastating floods, or excessive and debilitating
heat and parching drought, or sudden and unseasonable frost, or extreme
cold. And now, death and destruction come upon us or our property, at any
season, in the gale, the hurricane, or the tornado; or a succession of
sudden or peculiar changes blight our expected crops, and plant in our
systems the seeds of epidemic disease and death. These, and other normal
conditions, and varied changes, and violent extremes, potent for good or
evil, are continually alternating above and around us. They affect our
health and personal comfort, and, through those with whom we are
connected, our social and domestic enjoyments. They influence our business
prosperity directly, or indirectly, through our near or remote dependence
upon others. They limit our pleasures and amusements--they control the
realities of to-day, and the anticipations of to-morrow. None can
prudently disregard them; few can withhold from them a constant attention.
Scientific men, and others, devote to them daily hours of careful
observation and registration. Devout Christians regard them as the
special agencies of an over-ruling Providence. The prudent, fear their
sudden, or silent and mysterious changes; the timid, their awful
manifestations of power; and they are, to each and all of us, ever present
objects of unfailing interest.
This _interest_ finds constant expression in our intercourse with each
other. A recent English writer has said: "The germ of meteorology is, as
it were, innate in the mind of every Englishman--the weather is his first
thought after every salutation." In the qualified sense in which this was
probably intended, it is, doubtless, equally true of us. Indeed, it is
often not only a "first thought" _after_ a salutation, but a part of the
salutation itself--an offspring of the same friendly feeling, or a part of
the same habit, which dictates the salutation--an expression of sympathy
in a subject of common and absorbing interest--a sorrowing or rejoicing
with those who sorrow or rejoice in the frowns and smiles of an
ever-changing, ever-influential atmosphere.
If consistent with our purpose, it would be exceedingly interesting to
trace the varied forms of expression in use among different classes and
callings, and see how indicative they are of character and employment.
The sailor deals mainly with the winds of the hour, and to him all the
other phases of the weather are comparatively indifferent. He speaks of
airs, and breezes, and squalls, and gales, and hurricanes; or of such
appearances of the sky as prognosticate them. The citizens, whose lives
are a succession of _days_, deal in such adjectives as characterize the
weather of _the day_, according to their class, or temperament, or
business; and it is pleasant, or fine, or _very_ pleasant or fine;
beautiful, delightful, splendid, or glorious; or unpleasant, rainy,
stormy, dismal, dreadful or horrible. The farmer deals with the weather
of considerable periods; with forward or backward _seasons_, with "cold
snaps" or "hot spells," and "wet spells" or "dry spells." And there are
many intermediate varieties. The acute observer will find much in them to
instruct and amuse him, and will probably be surprised to find how much
they have to do with his "first impressions" of others.
But I have a more important object in view. I propose to deal with "The
PHILOSOPHY _of the Weather_"--to examine the nature and operation of the
arrangements from which the phenomena result; to strip the subject, if
possible, of some of the complication and mystery in which traditionary
axioms and false theories continue to envelop it; to endeavor to grasp
_its principles_, and unfold them in a plain, concise, and systematic
manner, to the comprehension of "_the many_," who are equal partners with
the scientific in its practical, if not in its philosophic interest; and
to deduce a few general rules by which its changes may be understood, and,
ultimately, to a considerable extent, foreseen.
This is not an easy, perhaps not a prudent undertaking. Nor is my position
exactly that of a volunteer. A few words seem necessary, therefore, by way
of apology and explanation.
In the fall of 1853, in the evening of a fair autumnal day, I started for
Hartford, in the express train. Just above Meriden, an acquaintance
sitting beside me, who had been felicitating himself on the prospect of
fine weather for a journey to the north, called my attention to several
small patches of scud--clouds he called them--to the eastward of us,
between us and the full clear moon, which seemed to be enlarging and
traveling south--and asked what they meant.
"Ah!" said I, "they are scud, forming over the central and northern
portions of Connecticut, induced and attracted by the influence of a
storm which is passing from the westward to the eastward, over the
northern parts of New England, and are traveling toward it in a southerly
surface wind, which we have run into. They seem to go south, because we
are running north faster than they. You see them at the eastward because
they are forming successively as the storm and its influence passes in
that direction, and are most readily seen in the range of the moon; but
when we reach Hartford you will see them in every direction, more numerous
and dense, running north to underlie that storm."
I had seen such appearances too many times to be deceived. It was so. When
we arrived at Hartford they were visible in all directions, running to the
northward at the rate of twenty-five miles an hour. In the space of forty
minutes we had passed from a clear, calm atmosphere (and which still
remained so), into a cloudy, damp air, and brisk wind blowing in the same
direction we were traveling, and toward a heavy storm. My friend passed
on, and met the southern edge of the rain at Deerfield, and had a most
unpleasant journey during the forenoon of the next day. Taking the cars
soon afterwards, in the afternoon, for the south, I found him on his
return.
"Shall I have fair weather now till I get home?" said he.
"There are no indications of a storm here, or at present," I replied, "but
we may observe them elsewhere, and at nightfall."
He kept a sharp look-out, and, as we neared New Haven, discovered faint
lines of cirrus cloud low down in the west, extending in parallel bars,
contracting into threads, up from the western horizon, in an E. N. E.
direction toward the zenith.
"Now, what is that?" said he.
"The eastern outlying edge of a N. E. storm, approaching from the W. S. W.
It is now raining from 150 to 200 miles to the westward of the eastern
extremity of those bars of cirrus-condensation; perhaps more, perhaps
less; and under those bars of condensation the wind is attracted, and is
blowing from the N. E. toward the body of the storm, and where the
condensation is sufficiently dense to drop rain. That dense portion will
reach here, and it will rain from twelve to fifteen hours hence. As we
pass along the shore, and run under that out-lying advance
cirrus-condensation, we shall see that the vessels in the Sound have the
wind from the N. E., freshening, but we shall continue to have this light
and scarcely-perceptible air from the northward for a time--_the N. E.
wind always setting in toward an approaching storm, out on the Sound, much
sooner than upon the land_."
As we approached the storm, and the storm us, the evidence of denser
condensation at the west, and of wind from the east, blowing toward it,
became more apparent. The fore and aft vessels were running "up Sound"
with "sheet out and boom off," before a fresh N. E. breeze, and my friend
was astonished.
"I must understand this," said he; "how is it?"
"All very simple. The page of nature spread out above us is intelligible
to him who will attentively study it. The laws which produce the
impressions and changes upon that page, are few and comprehensible.
Although there is great variety, even upon the limited portion which is
bounded by our horizon, there is also substantial uniformity; and,
although the changes are always extensive, often covering an area of one
thousand miles or more, and our vision can not extend in any direction
more than from thirty to fifty, yet those changes are always, to a
considerable extent, intelligible, and may often be foreseen."
"Has meteorology made such progress?"
"By no means. It has, indeed, been raised to the dignity of a science, and
professorships endowed for its advancement. Some books have been written,
and many theories broached in relation to it; and innumerable observations
of the states of the barometer and thermometer, of the clouds, and the
quantity of fallen rain, and the direction and force of the wind--made and
recorded simultaneously in different countries--have been published and
compared; and a great many important facts established, and tables of
'_means_' constructed, and just inferences drawn, yet the _few and simple
arrangements_ upon which all the phenomena depend, and _their philosophy_,
have not yet been clearly elicited or understood."
"Have not the 'American Association for the Advancement of Science'
arrived at some definite and sound conclusion upon the subject?"
"No; it has been with them, for many years, an interesting subject for
papers and debate. Some very valuable articles, upon particular topics, or
branches of the subject, have been read and published. But the
_Cyclonologists_, as they term themselves, and who seem to think the great
question is, '_Are storms whirlwinds?_' appear with new editions and
phases of their favorite views as regularly as the annual meeting recurs;
and, though they have not convinced, they seem to have silenced their
opponents. The only conclusion, however, judging from their debates, to
which the Association appear to have come with any considerable unanimity,
is, that they are yet without sufficient _authentic observations_ and
well-established facts, to authorize the adoption of the Huttonian,
Daltonian, Gyratory, or Aspiratory, or any of the other numerous theories
which abound. And they are right. The subject is mystified by these
theories and speculations of the study, founded on barometrical and
thermometrical records, and the direction and force of the surface winds.
"The qualities of heat were among the earlier discoveries of science, and
all the phenomena of the weather were forthwith attributed to its
influence. Hastily-formed and erroneous views of its power, and the manner
of its action in particular localities, and under particular
circumstances, have retained the credence accorded to them when first
announced, although subsequent discoveries have shown their fallacy; some
new theory of _modification_ having been invented to reconcile the
discrepancies as soon as they appeared. Perhaps it is not too much to say
(however it may seem to one not thoroughly acquainted with the subject,
who does not know that the _primary_ and secondary modifying hypotheses
found in Kaemtz, may be counted by hundreds) that there is not remaining in
any other science, and possibly in all others, an equal amount of false
and absurd theory, and of forced and unnatural grouping of admitted facts
to sustain it, as in meteorology as at present taught and received.
Astronomy, as a science, is almost perfected--the nature, and size, and
orbits, of the distant worlds around us are known--while constant changes
and alternating atmospheric conditions, which all occur _within less than
six miles of us_, affecting all our important interests, and obvious to
our senses, although much talked off, and made the objects of many
theories, are but little understood."
"How, then, did you acquire the information you seem to possess?"
"By studying '_the countenance of the sky_,' for in no other way has such
information ever been, or can it ever be, acquired. By a long-continued,
daily, and sometimes hourly observation of the clouds and currents of the
atmosphere, in connection with such reports of the then state of the
weather elsewhere, as have fallen under my notice, and the effect of its
changes upon the animal creation--for very much can be learned from them.
Yonder flock of black ducks that sit on that inshore rock, above the
tide--the wildest and most suspicious of all their tribe--although the
air is calm about them, know well that a storm is at hand. They probably
both see and feel it. As twilight approaches they will fly away inland,
forty or fifty miles perhaps, and settle among the lilies or grass which
surround some fresh-water pond, certain of remaining while the storm
lasts, and for one day at least, out of danger, and undisturbed. Many a
time, in my boyhood, have I heard, in the stillness of evening, the
whistling of their wings, as they swept up the Connecticut valley, to
seek, on the borders of the coves, and in the creeks of the meadows, a
concealed and safe feeding-place during a coming storm. And many a time in
the autumn, after they had all passed down for the season, when the
indications of an approaching storm were clearly visible at nightfall,
have I waited for them to return, on the eastern margin of a bend in the
cove, on the eastern side of a creek, to shoot them, though invisible, by
shooting across the head of the wake, which they made upon the water in
alighting, and from which the few remaining rays of twilight that came
from the western sky were reflected.
"But I am far from being singular in this. That page is more extensively
read than is generally supposed. Many plain, unassuming men--farmers,
shipmasters, and others within the circle of my acquaintance--know more,
practically, of the weather than the most learned closet-theorist, or the
most indefatigable recorder of its changes. Every one, by studying the
page of nature above him, as he would the page of any other science, and
testing, by observation, the numerous theories invented to account for the
varied phenomena, may learn much, very much, that will be useful and
interesting to him, and which he can never learn from books, or
instruments, or theories alone."
"Well," said my friend, "I am too far advanced in life, as are many
others, to commence such observations, and you must publish."
I demurred, and he insisted.
"It is difficult to spare the time; and I can not neglect my profession,"
I urged.
"Where there is a will there is a way," he replied.
"It is difficult to make one's self understood without many
illustrations."
"Very well, they are easily obtained."
"But they cost money, and it is said 'science will not pay its way' like
fiction and humbug."
"That," said he, "is a libel--such science will. Every one is interested
in the weather--all talk about it--and thousands would carefully observe
it, if they could be correctly guided in their observations."
"I may get into unpleasant controversy."
"Suppose you do; you can yield your position if wrong, and maintain it if
right, and _magna est veritas_."
"But I may be mistaken in some of the views to which it will be necessary
to advert, if I attempt to systematize the subject."
"Be it so--your mistakes may lead others to the discovery of the truth.
Besides, the weather is _common property_, and every one has a right to
theorize about it, or to talk about it, as they please--even to call a
stormy day a pleasant one, or make any other mistaken remark concerning
it; and every other person is entitled to a like latitude of reply. And
further," said he, with some emphasis, "no important observation, in
relation to a subject of such interest, should be lost; and, if you have
observed one new fact, or drawn one new and just inference from those
which have been observed by others; and especially if, from observation
and reading, you can deduce from the phenomena an intelligible,
_observable, general system_, it is not only your right, but duty, to make
it known. Such a knowledge of the true system is greatly desired by every
considerate man."
To my friend's last argument I was compelled to yield. I could make no
reply consistent with the great principles of fraternity, which I shall
ever recognize. The promise was given. My friend went on his way, and I
went to the daguerreotypist to procure a copy of the then appearance of
the sky, as the first step toward its fulfillment. The fulfillment of that
promise, reader, you will find in the following work. It was commenced as
an article for a magazine, but it has grown on my hands to a volume.
Justice could not well be done to the subject in less space. It has been
written during occasional and distant intervals of relaxation from
professional avocations, or during convalescence from sickness, and it is,
for these reasons, somewhat imperfect in style and arrangement. But I have
no time to rewrite. There is much in it which will be old to those who
read journals of science, but new to those who do not. There is more which
will be new to all classes of readers, and may, perhaps, be deemed
heretical and revolutionary by conservative meteorologists; yet I feel
assured that the work is a step in the right direction--that it contains a
substantially accurate exposition of the Philosophy of the Weather, and
valuable suggestions for the practical observer.
I have inserted my name in the title-page, contrary to my original
intention, and at the suggestion of others; for I have no scientific
reputation which will aid the publisher to sell a copy. Nor do I desire to
acquire such reputation. It can never form any part of my "capital in
life." Nor has it influenced me at all in preparing the work. I have aimed
to fulfill a promise, too hastily given, perhaps--to put on record the
observations I have made, and the inferences I have drawn from those of
others--to induce and assist further observations, and, if possible, of a
_general_ and _connected character_--and to impress those who may read
what I have written with the belief, that _they will derive a degree of
pleasure from a daily familiarity with, and intelligent understanding of,
the "countenance of the sky," not exceeded by that which any other science
can afford them_.
I have examined, with entire freedom and fearlessness (but I trust in a
manner which will not be deemed censurable or in bad taste) the theories
and supposed erroneous views of others, for, in my judgment, the
advancement of the science requires it. Says Sir George Harvey, in his
able article on Meteorology, written for the Encyclopaedia Metropolitana:
"It is humiliating to those who have been most occupied in
cultivating the science of meteorology, to see an agriculturist or a
waterman, who has neither instruments nor theory, foretell the future
changes of the weather many days before they happen, with a precision
which the philosopher, aided by all the resources of science, would
be unable to attain."
The admissions contained in this paragraph, in relation to the comparative
uselessness of instruments and theories, and the value of practical
observation, are both in a good measure true. And the time has come, or
should speedily come, when "_pride of opinion_," and "_esprit du corps_,"
among theorists and philosophers, should neither be indulged in, nor
respected; and when their theories should be freely discussed, and rigidly
tested by the observations of practical men. Such measure, therefore, as I
have meted, I invite in return. Let whatever I have advanced, that is new,
or adopted that is old, be _as_ rigidly tested, and _as_ freely discussed.
Let the errors, if there be any--and doubtless there are--be detected and
exposed. Let the TRUTH be sought by all; and meteorology, as a PRACTICAL
SCIENCE, advance to that full measure of perfection and usefulness, of
which it is unquestionably susceptible.
TABLE OF CONTENTS.
PAGE
CHAPTER I.
Heat and moisture are indispensable to the fertillity of the
earth--Arrangements exist for their diffusion and distribution,
and all the phenomena of the weather result from their
operation--Heat furnished or produced mainly by the direct
action of the sun's rays--Manner in which it is diffused over
the earth--Other causes operate besides the sun's rays--The
earth intensely heated in its interior--Heat derived from the
great Oceanic currents, and the aerial currents which flow
from the tropics to the poles, and from magnetism and
electricity--Water distributed by an atmospheric machinery as
extensive as the globe--Evidences of this--Its distribution over
the continents of North America--Explanation of it--Source from
whence our supply of water is derived, and from which our rivers
return 1
CHAPTER II.
Our rivers return in the form of clouds, and in storms and
showers--Definition and character of storms--Differences in
the character of the clouds which constitute them--Nomenclature
of Howard--Its imperfections--New order of description--Low
fog--High fog--Storm fog--Storm scud--N. W. scud--Cumulus--
Stratus--Cirrus--Compounds of the two latter--recapitulation in
tabular form 24
CHAPTER III.
Our rivers do not return from the North Atlantic--All storms and
showers move from the westward to the eastward--Seeming clouds
seen moving from the eastward to the westward are scud--They are
incidents of the storm, and not a necessary part of it--The
storm clouds are above them, moving to the eastward--Occasions
when this may be seen--Admitted facts prove it--Investigations
prove it--May be known from analogy--From the fact that there is
an aerial current pursuing the same course in which the storms
originate--Character of this current--Its influence upon our
country--Importance of a knowledge of its origin, cause, and the
reciprocal action between it and the earth--To this end necessary
to go down "to the chambers of the South" 43
CHAPTER IV.
The trade wind region--Its extent and arrangements--Its belt of
daily rains and movable character--The trade winds--The extra
tropical belt of rains--Connection between them and their annual
movements--The counter-trades--Their origin and situation--One
of them constitutes our aerial current--It originates in the
South Atlantic as a surface-trade--Anomalies of the trade wind
region--Dry seasons--Humboldt's description of them--Exist where
the surface trades are situated--The rainless countries--
Concentrated counter-trade--Monsoons--Received theory in relation
to them a fallacy--Cause of the great central phenomena--
Calorific theory a fallacy--Land not hotter under the belt of
rains, nor sea materially so--Theory should be abandoned 52
CHAPTER V.
The agent, magnetism--Its character and currents--Oxygen
magnetic--Precipitation at the belt of rains occasioned by
depolarization--Storms originate in this central belt, and move
toward the poles 82
CHAPTER VI.
Course and functions of the counter-trade--Ours come from the
South Atlantic--Reason why it can not come from the Pacific--
Mistake of Mr. Redfield and Lieutenant Maury in regard to it--
All our storms originate in it--Proofs of this--State of the
weather, whether hot or cold affected by it--Proofs of this--All
our surface winds are incidents of it, and due to its conditions
and attractions--Proofs of this--Character of the different
winds--Anomalies of Mr. Blodgett accounted for--Received theory
in regard to sea and land breezes a mistaken one--Proofs of
this--Peculiar character of the N. W. wind--Identity with the
winter Mexican northers--Character of the West India hurricanes--
Of the thunder-gust--Of the tornado--Sundry particulars in
relation to the latter--Due to currents of electricity--
Proportions of winds in different localities--Examination of the
work of Professor Coffin upon that subject--Examination of
Lieutenant Maury's theory of the monsoons 92
CHAPTER VII.
Height of the counter-trade in different latitudes--Cause of the
Calms of Cancer--Influence of mountains upon the counter-trade--
Reports of Herndon and Gibbon--Focus of precipitation in the
extra-tropical belt north of its southern line--Evidences of
this--The elevation of the counter-trade above the earth varies
in the same latitude with the variations in the phenomena of the
weather--Temperature of the counter-trade--Rain dust, its origin
and indications--Volcanic ashes--How far they indicate its course
of progression--Question whether there is an eastern progression
of the body of the atmosphere above the machinery of distribution 179
CHAPTER VIII.
Important to understand the precise character of the reciprocal
action between the earth and the counter-trade--Connection
between the width and movements of the belt of inter-tropical
rains and the volume of the trades--Its peculiarities over
Africa, the Atlantic, and South America--The magnetic equator--
Character of the storms which originate in the inter-tropical
belt indicate local magnetic action--Supposed influence of
volcanic action--Gulf Stream changes its position--This the
result of magnetic action--Alternating contrasts of heat and
cold, and rain and drought--Dr. Webster's history of the
weather--Spots upon the sun--Their character and influence--Cold
or warm periods during the same decade, and during different
decades--Connection between the spots and magnetic disturbances
and variations--Influence of the moon upon the weather--No
decisive inference to be drawn from these facts, and a more
critical examination necessary 204
CHAPTER IX.
Examination of existing theories--Calorific theory the prevailing
one--Lateral overflow of Professor Dove--Absurdity of his views
in relation to them--His theory of hurricanes--Its absurdity--A
new theory by Mr. Dobson--Three theories advanced by
meteorologists of this country--Professor Espy's theory--Mr.
Bassnett's theory--Mr. Redfield's theory--Extended examination of
the latter--His theory in relation to the fall of the barometer
contradictory in its character--Philosophy of the barometric
change--No aid to be derived from these theories 232
CHAPTER X.
Further inquiry in relation to the reciprocal action between the
earth and the counter-trade--Terrestrial magnetism, and what we
know of it--Its elements, and their variations--Their connection
with the variations of atmospheric condition--Magnetism acts
through its connection with electricity--Character of the latter
and its variations--Their connection with atmospheric conditions--
Electricity as well as magnetism in excess over this country--
Effects of it upon our climate--Closer consideration of the
atmospheric phenomena--Their diurnal changes and connections
compared with those of magnetism and electricity--Grouping of all
the diurnal variations--Particular and separate examination of
them--Classification of storms--Examination in detail of the
several classes and the primary influence of the earth or
counter-trade in relation to each 285
CHAPTER XI.
Prognostics 340
THE PHILOSOPHY OF THE WEATHER.
CHAPTER I.
Heat and moisture are indispensable to the fertility of the earth. Without
suitable arrangements for their diffusion and distribution, and within the
limits of certain minima and maxima, it would not have been habitable, or
the design of its Creator perfected. These arrangements therefore exist,
and "while the earth remaineth seed time and harvest shall not cease." Few
and simple in their character, though necessarily somewhat complicated and
irregular in their operation, the ultimate result is always attained. A
beautiful system of compensations supplies the losses of every apparent
irregularity in one section or crop, by the abundance of others.
From the operation of these few, simple, connected, and intelligible
arrangements for the diffusion of heat and the distribution of moisture
over the earth, result all the phenomena which constitute the weather; and
by studying them, and their operation, we may acquire an accurate
knowledge of its "_Philosophy_."
The necessary heat is furnished, or produced, mainly by the direct action
of the sun's rays; and the most obvious feature in the arrangements for
its diffusion is that by which the sun is made to shine successively and
alternately upon different portions of the earth. Nothing animate or
organic could endure his burning rays, if they shone continuously or
vertically upon one point, or could exist without their occasional
presence. Hence the provision for a diurnal rotation, to prevent the
exposure of any portion of the globe to the action of those rays for
twenty-four consecutive hours, except for a limited period, and at a
considerable angle, in the polar regions. But the earth is spheroidal, and
a diurnal revolution would still leave that portion which lies under the
equator too much, and the other too little, exposed to the action of the
sun. This is obviated by an annual revolution of the earth around the sun,
and an obliquity of its axis, by reason of which the northern and southern
portions are alternately and, as far as the tropics vertically, exposed to
the sun; and it is made to travel (so to speak) from tropic to tropic,
producing summer and winter, and other important phenomena.
This obliquity and consequent change of exposure are in degree precisely
what the wants of the earth would seem to require. If it was greater, the
sun would travel further north and south, but the alternate winters would
be longer and more severe. If it was less, the end would not be as
perfectly attained.
The direct action of the sun's rays upon the earth, particularly those
portions which lie north and south of the tropics, is not the only source
from which the supply of heat is derived. Although there is a general
increase of heat in spring and summer when the sun travels north, and of
cold when he travels south in winter, yet there are frequent
irregularities attending both. Very sudden and great changes occur in each
of them. Frost sometimes, cool weather often, occurs in midsummer, and
considerable heat and tornadoes in midwinter. And ordinarily the maxima
and minima of each month and, indeed, of each week are widely apart. Even
in the polar regions, in midwinter, _where the sun does not shine at all_,
the same moderating changes with which we are conversant occur in degree.
An extract or two from the register found in Dr. Kane's narrative of the
"Grinnell Expedition" will illustrate this.
JANUARY 1851, (LATITUDE ABOUT 74 deg., LONGITUDE ABOUT 70 deg.).
Date. Wind. Force. Ther. Bar. Sky and Weather.
Jan. 3 calm -26.1 29.62 blue sky, m.
" 4 W. gent breeze -21.3 29.53 blue sky,
detached clouds, m.
" 5 W. by N. gent breeze -3.9 29.59 blue sky, m.,
clouded over.
" 6 W. by S. light breeze -0.8 29.67 clouded over, m.,
snow.
" 7 W. gent breeze -14.4 29.96 blue sky, detached
clouds, m.
" 8 W.S.W. light air -21.2 30.14 blue sky, m.
" 29 W.N.W. light air -18.9 30.19 blue sky.
" 30 NW. by W. light air -13.5 30.17 clouded over, m.
" 31 NW. by W. gent breeze -4.4 29.35 clouded over, snow.
Feb. 1 W. light breeze -11.7 29.27 cloudy, blue sky, m.
" 2 W. light air -25.1 29.62 blue sky, detached
clouds, m.
These extracts are instructive. It will be seen that on the 3d of
January, when the sun had been absent some weeks, it was calm, the
thermometer stood at 26 deg. below zero (the - or minus mark before the
figures indicates that), and the barometer at 29.62, with blue sky,
somewhat misty or hazy--(the letter "m." standing for misty or hazy)--a
state of the air which existed most of the time when it did not snow or
rain, and therefore is of no importance in this connection. The next day
the thermometer began to rise, and the barometer to fall. On the 5th it
clouded over, and the thermometer rose rapidly, and on the 6th it had
risen more than 25 deg., and snow fell. On the 7th it cleared off, the
thermometer fell rapidly, and the barometer rose. On the 8th the
thermometer had fallen to 21 deg. below zero, and the barometer had risen to
30.14. Another instance, in all respects similar, occurred the latter part
of the month. We shall see hereafter that these changes are precisely like
those which occur with us, and every where. That, as in the polar regions,
and whether the sun be present or absent, or obscured by clouds, and by
night as well as by day, the changes from warm to cold and from cold to
warm are sudden and great, and that the latter are connected with the fall
of rain and snow--that every where in winter it _moderates to storm_.
Many other instructive instances, especially in relation to the great
difference in the seasons in our own country, and upon the same parallels
elsewhere, might be cited if it were necessary. But they will more
appropriately appear in the sequel.
[Illustration: Fig. 1.
In the above cut the isothermal lines are Centigrade. The zero of the
Centigrade thermometer is the freezing point of water, or 32 deg. of
Fahrenheit. The boiling point of water is 100 deg. Centigrade, or 212 deg.
Fahrenheit. A degree of Centigrade is equal to one degree and four-fifths,
Fahrenheit. The 0 deg. line of the cut, therefore, is 32 deg. of Fahrenheit--the
line of 5 deg. above is 41 deg. Fahrenheit--the line of 5 deg. below is 23 deg.
Fahrenheit, and so on. The reader, who is not familiar with the difference
in the scale of the thermometer, is desired to remember this; for we shall
make occasional extracts in which the temperature is given in the
Centigrade scale.]
The cause of those irregularities, especially in the same seasons of
different years, and when very great, is often sought and supposed to be
found in the presence or absence of spots on the sun, ice floes and bergs
in the Atlantic, etc., etc. But neither the spots, nor ice, nor other
local causes produce them. The cause will be found in the character of the
arrangements we are considering, and the irregular action of the power
which controls them.
Nor is the temperature of the northern hemisphere, north of the tropics,
equal in the same latitudes. Very great diversities exist in the "annual
mean" as well as the "mean" of the different seasons. Accurate
observations at many points have enabled men of science to demonstrate
this by drawing isothermal lines (_i. e._, lines of equal average annual
heat) from point to point around the earth, which show at a glance these
differences. The annexed cut is a polar projection of the isothermal lines
of the northern hemisphere, as far down as the tropic, copied from
Kaemtz's Meteorology. The dotted lines show the parallels of latitude, the
dark lines the isothermal lines, or lines of equal annual average
temperature. The reader is desired to observe how rarely they correspond
with the parallels of latitude, and how they fall below in a few
instances, and in others with great uniformity rise almost to the pole.
Take, for example, the isothermal line of 0 or zero--that is, the line
where the mean or _average_ height of the thermometer _for the year_ is at
zero. At Behring's Straits this line is a little below the Arctic circle,
or the parallel of 66.30 north latitude. Passing east over North America,
it descends into Canada, almost to Lake Superior, and to about the 50th
parallel: that is to say, it is on an average during the year as cold on
our continent at the 50th parallel as it is near Behring's Straits at the
65th parallel. Passing east, the line of zero rises again over the
Atlantic Ocean until, in the meridian of Spitzbergen, it reaches, within
the Arctic circle, up almost to the 75th parallel. So, too, the isothermal
of 5 deg. below zero, which is below the 60th parallel in Siberia, rises in
the North Sea, above Behring's Straits, to the parallel of 75 deg., descending
on the continent in North America to the 55th parallel, and rising again
almost to the pole at Spitzbergen, to descend again in Siberia, while the
isothermals of 10 deg. and 15 deg. below zero, which in North America are but just
above the latitude of 60 deg. and 75 deg. respectively, ascend abruptly
_surrounding the magnetic pole_, and _falling short of the geographical
one_. Let this projection of the lines of equal temperature, and
particularly the situation of the magnetic poles, be studied well, for we
shall recur to it hereafter in illustration of many important portions of
our subject.
It is apparent from these facts, and were it necessary might be rendered
still more so by referring to others, that other causes operate in the
distribution of heat over the earth besides the direct action of the sun's
rays upon it. Doubtless very considerable allowance is to be made for the
difference of seasons, and difference during the same season upon the
land and upon the ocean; in mountainous countries and level ones. But
making every allowance for them, the fact that other causes have a
_controlling_ influence in producing the deviations still remains most
obvious. Neither the difference of temperature between the land and the
ocean, or land surfaces of unequal elevations, will account for the
elevation of the isothermal lines on different portions of the ocean, or
their extension around the magnetic poles.
Returning to a consideration of the arrangements for the diffusion of
heat, we observe: First, that the earth itself is intensely heated in its
interior. This is inferred, and justly, from the fact that the thermometer
is found to rise about one degree for every fifty-five feet of
descent--whether in boring artesian wells, exploring caves, or sinking
shafts in mines. It is demonstrated, also, by the existence of hot springs
and the action of volcanoes. Heat is supposed to be conducted from the
center toward the surface every where, but with difficulty and slowly. It
is also supposed to be conducted from the tropical regions toward the
poles. Such is the opinion of Humboldt. (Cosmos, vol. i. p. 167.)
Probably it reaches the surface and exerts an influence, also, upon the
weather through the ocean, and by heating it in its greatest depths.
Little attention has been paid, so far as I am informed, to the question
how far the ocean is thus heated in _tropical latitudes_. Doubtless a
portion of the warmth of the ocean there is derived from that source, and
it has its influence in changing the temperature of the deep-seated cold
polar currents of, the great oceans. Perhaps it may yet be found that the
icebergs are detached by it in the polar seas--the observations of Dr.
Kane point to such a result. (Grinnell Expedition, p. 113, and also chap.
48.)
Little need be said of the inconsiderable quantities of heat supposed to
be derived by radiation from the stars, the planets, and from space. If
any such are derived they are too inconsiderable to be of importance in
this inquiry.
Heat is also carried, and in quantities which exert very considerable
influence upon the weather, from the tropics to the poles by the great
oceanic currents which flow unceasingly from one to the other.
The most important of these with which we are acquainted is the Gulf
Stream of the Atlantic. Gathering in the South Atlantic, and passing north
through the Caribbean Sea and the Gulf of Mexico, it issues out through
the Bahama Channel, and flows north along the eastern coast of the United
States, but some distance from it, to Newfoundland, and from thence
continuing to the north-east and spreading out over the surface of the
ocean--a portion of it mingling with the waters of the North Atlantic in
passing--it flows up on the western coast of Europe, around the Faroe
Islands, and Spitzbergen, to the polar sea; passing around Greenland, and
perhaps through its Fiords, it descends again through the sounds and
channels of the Arctic regions into Baffin's Bay, and through Davis's
Straits, burdened with the icebergs and floes of the polar waters, to
return again to the South Atlantic. For reasons which will appear in the
sequel, it has comparatively little influence upon the weather of the
United States. Western Europe, however, Greenland, the islands which lie
in its course, and the polar seas, are most materially influenced.
Although not the only cause, it has very much to do with the remarkable
elevation of the isothermal lines over the Northern Atlantic, and upon
Western Europe, as seen upon the map.
A like oceanic current exists in the Pacific Ocean, the influence of which
may also be traced upon the map by the elevation of the isothermal lines
at the northern extremity of that ocean, and upon the north-west coast of
North America. A vast amount of heat is transported from the tropical to
the temperate and frozen regions of the earth by these great oceanic
currents.
Another supply is derived from aerial currents which flow from the tropics
toward the poles. These currents exist every where over the entire surface
of the earth, but in more concentrated volumes along the great "lines of
no variation," and greater magnetic intensity, on the western side of the
great oceans, over the eastern portions of the two continents of North
America and Asia. Not, as meteorological writers suppose, in the upper
portions of the atmosphere, having risen in the trade-wind region and run
off at the top toward the poles by force of gravity, but near, and
sometimes in contact with the earth. The influence of these aerial
currents upon the temperature of the atmosphere, and in producing the
phenomena we are to consider, is exceedingly important. We shall have
occasion to examine them with great care and minuteness under another
head, for upon them, more than any other portion of the arrangements,
depend not only the diffusion of heat, but also the distribution of
moisture.
Still another supply of heat, during the sudden changes, at least, is
produced by the action of terrestrial magnetism and electricity. Very
great progress has been made within a short period, in the investigation
of the nature of these agents. The identity, or at least intimate
association or connection of heat, light, electricity, and magnetism,
always suspected, has been in various ways, and by a variety of
experiments demonstrated. The influence of magnetism if distinct from
gravitation, is second only to that; and its agency in producing the
phenomena we are considering is primary and controlling. We will only, in
this connection, ask the reader to note the situation of the north
magnetic poles (for there are two of them); the manner in which the
isothermal lines _surround_ them; the fact that they are _poles of cold_,
_i. e._, that it is colder there than even to the north of them. We shall
recur to this part of the subject again.
Such, briefly considered, are the principal arrangements by which heat is
diffused over the earth.
Equally marked by infinite wisdom, and equally interesting and important,
are the arrangements by which moisture is distributed. Doubtless the
general belief is that this is a simple process; that water evaporates
and rises till it meets a colder stratum of atmosphere, and then condenses
and falls again; or that, according to the Huttonian theory, currents of
air of different temperatures mingle and equalize their heat, and the
aggregate mass when equalized in temperature is cooler, and therefore is
unable to hold as much moisture in solution as the most heated portion
had, and the excess falls in rain. But the process is by no means so
simple, nor is heat the sole or most powerful agent concerned in it.
Currents of air do not mingle, but stratify. Evaporation from the surface
of any given portion of the earth outside of the tropics does not alone
supply that portion with rain. _Vast and wonderful, coextensive with the
globe itself, and perfectly connected, is the machinery by which that
supply is furnished even to the most inconsiderable portion of its
surface._
Take your map of North America and note, in this respect, its
peculiarities. It extends from the Isthmus of Darien to the Arctic
regions, and from the 65th to the 160th meridian of west longitude from
Greenwich, and has upon its surface a type of every climate in the world.
For the purpose of simplifying and illustrating the matter in hand, let us
divide it into five sections. Let the first section embrace Central
America and Southern Mexico, south of 28 deg.; the second, Northern Mexico and
Southern New Mexico, California, etc., between the parallels of 28 deg. and
32 deg.; the third, Northern California, Utah, Southern Oregon, and Western
New Mexico, north of the parallel of 32 deg.; the fourth, the entire
continent north of 42 deg.; and the fifth, the eastern United States, east of
the meridian of 100 deg.. These divisions are not intended to be entirely
accurate in their separation, but substantially so for the purpose of
illustrating the differences which exist in each.
The accompanying diagram shows approximately, by dotted lines, the
divisions.
[Illustration: Fig. 2.]
Now let us see in what a diverse manner, and to what a different extent,
they are severally supplied with moisture.
Central America and Southern Mexico lie within the tropics--their rains
are tropical rains. The season is divided into wet and dry, as are the
seasons of all tropical countries which are not rainless. During the rainy
season it rains a portion of nearly every day, and during the dry season
the sky is clear, the air is pure, and rain seldom falls.
All around the earth within the tropics, over the land and over the sea,
there is a belt of almost daily rains, varying in width, north and south,
in different sections, but averaging about five hundred miles. This belt
of daily rains is formed at and by the meeting of N. E. and S. E. trades,
and travels north and south with them, as they do with the sun,
_encircling the globe_. By this narrow belt a portion of the earth's
surface, an average of some 35 deg. of latitude, is supplied with moisture.
Wherever it is situated at any given period, the tropical rainy season
exists; and when it is absent in its northern or southern transit, the dry
season prevails. Southern Mexico is within the range of this moving belt,
and in its course to the northward with the sun, in our summer from May to
October, it arrives over, and covers that country with a rainy season.
When the sun returns to the south, taking with it the trades and this belt
of tropical rains, that portion of Mexico is without rain, and dry, and so
continues until the rainy belt returns in the following year. While the
belt is over Southern Mexico it is nearly all _precipitation_, and there
is little _evaporation_; while that belt is _absent_ it is all
_evaporation_, with little or no _rain_. Surely this is not consistent
with the prevailing belief of simple evaporation, ascent to a colder
stratum, commingling, and condensation, and rain. Southern Mexico at least
is not supplied by mere evaporation from its surface, and must therefore
form an exception to that belief, and to the Huttonian theory.
But we shall recur again to the peculiarity of distribution within the
tropics.
Turn now for a brief space to Northern Mexico, Southern New Mexico, and
Southern California. In Northern Mexico, Southern New Mexico, Utah, and
California, between the parallels of 28 deg. and 32 deg., and particularly west of
the mountain ranges, we find an almost rainless region, sterile and
worthless, resembling that which is found upon nearly the same parallels
of north latitude in Northern Africa, Egypt, Arabia, Beloochistan,
Afghanistan, and North-western India; and in corresponding latitudes south
of the Equator, in Peru, a portion of Southern Africa, and the northern
and middle portions of New Holland. Why Northern Mexico and the other
countries named are thus sterile and comparatively rainless, we shall see
hereafter, when we examine critically the machinery of distribution as it
operates within the tropics. It is the fact that it is thus sterile and
rainless to which we desire to call attention in this place.
Mr. Bartlett thus describes it:
"On leaving the head waters of the Concho, nature assumes a new
aspect. Here shrubs and trees disappear, except the thorny chaparral
of the deserts; the water-courses all cease, nor does any stream
intervene until the Rio Grande is reached, three hundred and fifty
miles distant, except the muddy Pecos, which, rising in the Rocky
Mountains, near Santa Fe, crosses the great desert plain west of the
Llano Estacado, or Staked Plain.
"From the Rio Grande to the waters of the Pacific, pursuing a
westerly course along the 32d parallel, near El Paso Del Norte, there
is no stream of a higher grade than a small creek. I know of none but
the San Pedro and the Santa Cruz--the latter but a rivulet, losing
itself in the sands near the Gila--the other but a diminutive stream,
scarcely reaching that river. At the head-waters of the Concho,
therefore, begins that great desert region, which, with no
interruption save a limited valley or bottom-land along the Rio
Grande, and lesser ones near the small courses mentioned, extends
over a district embracing sixteen degrees of longitude, or about a
thousand miles, and is wholly unfit for agriculture. It is a
desolate, barren waste, which can never be rendered useful for man or
beast, save for a public highway."--_Bartlett's Personal Narrative_,
vol. i. p. 138.
Turning now to Central and Upper California, and Utah, and Southern
Oregon, we find still another peculiarity. Like Southern Mexico, they have
a rainy and dry season, but at a different period, and for a different
reason. The dry season of California, etc., is the summer of the northern
hemisphere, and her rainy season the winter. _California_ is, therefore,
_dry_ when Southern _Mexico_ is _wet_, and _vice versa_. The belt of rains
which supplies California with moisture during her rainy seasons is the
belt of _extra-tropical_ rains, which extends from the northern limit of
the north-east trades to the poles, encircling the earth. The southern
edge of this extra-tropical belt is _carried up_ on the western coast of
America, and in that portion of the continent in _summer_, when the sun
and trades, and the inter-tropical rainy belt travel to the north, and
uncover California, etc., leaving them without rain for a period of about
six months.
[Illustration: Fig. 3. IN SUMMER.]
As the sun, with the trades, travels south, the southern edge of the belt
of extra-tropical rain follows, and covers California, etc., again
extending gradually from the north to the south, and thus their wet
season returns. The annexed diagrams by the shading will show the
situation of the rainy belts which cover Mexico, Utah, New Mexico, and
California in summer and winter, and that the belts of rains are entirely
distinct and different in character.
[Illustration: Fig. 4. IN WINTER.]
Here again in this section of the continent, as in Mexico, evaporation is
going on for six months of the year, and were it not for the return of the
belt of rains from the north, in the fall, would go on for the entire year
without precipitation; and for the other six months precipitation is
vastly in excess. Nor can this be reconciled with, or explained by, the
Huttonian or any other received theory of rain. Here again it is obvious
that evaporation alone, however great or long continued, will not furnish
the evaporating section with rain.
The northern portion of the continent lies beneath the zone of
extra-tropical rains, and north of the northern limit of the N. E.
trades--is never uncovered from it, and has no distinct rainy or dry
season, although more rain falls at certain periods, and in certain
localities, than at others. The climate of that part of Oregon which lies
upon the Pacific, and the character of its rains, resemble those of
North-western Europe, and will be further explained hereafter.
Coming to the portion of the continent which we occupy, the 5th section,
we find it different still--a most favored region. Portions of it--Eastern
Texas, for instance--are upon the same parallels of latitude as the
rainless regions of Northern Mexico, etc. Eastern Texas, however, is not
rainless. Other portions are upon the same parallels as California, etc.,
yet have no distinct rainy and dry season. We repeat, this section is a
most favored region--without a parallel upon any portion of the earth's
surface, except, in degree, in China and some other portions of Eastern
Asia.
It is not only without a distinct rainy and dry season, but it is watered
by an average, annually, of more than forty inches of rain, while Europe,
although bounded on three sides by seas and oceans, and apparently much
more favorably situated, receives annually an average of only about
twenty-five--if we except Norway, and one or two other places, where the
fall is excessive. The distribution of this supply of moisture over the
United States is, in other respects, wonderful. Iowa, in the interior of
the continent, far away from the great oceans, on the east or west, or the
Gulf of Mexico on the south, receives fifty inches; some ten or fifteen
inches more than fall upon the slope east of the Alleghanies, and
contiguous to the great Atlantic (from which all our storms are,
erroneously, supposed to be derived), and the average over the entire
great interior valley is about forty-five inches, falling at all seasons
of the year.
Observe, then, by way of recapitulation: Southern Mexico has a rainy
season furnished by the belt of _inter_-tropical rains, which _travels up
over it from the south_ in summer. California has a rainy season, which is
furnished by the _extra_-tropical belt of rains, which travels _down from
the north_, and covers it in winter. Northern Mexico and the adjoining
regions west of the 100th meridian are between the limits of the two, and
neither travels far enough to reach them, except for brief and uncertain
periods; they are comparatively rainless; while the eastern portion of
the continent, _in all latitudes_, unlike the others, is without a
distinctly marked dry season, or a rainless region, and with the exception
of occasional droughts, is abundantly supplied with rain at all seasons of
the year.
And now, what is the explanation of all this? What produces the
extra-tropical belt of regular rains surrounding the earth, north of the
parallel of 30 deg. north, in some places, and 35 deg. in others, extending to the
pole, with its southern edge traveling up ten or more degrees in summer,
leaving large portions of the earth subject to a dry season; and back
again in the winter to give them a rainy one? What produces the narrow
belt of inter-tropical rains, encircling the earth; traveling up and down
every year over an average of 35 deg. of latitude, supplying every portion of
it alternately with rain? And what connects the two together over the
eastern portion of North America, so as to leave no distinctly marked wet
and dry season, and no rainless and sterile portion there? Are all these
the result of simple evaporation, ascent to a colder region, condensation,
and descent again? Demonstrably not. Of the forty inches which fall
annually upon the middle and eastern portions of the United States, an
average probably of one-half or twenty inches, runs off by the rivers to
the ocean, or is carried away eastward by the westerly and north-westerly
evaporating winds. The same is true, in degree, of the rain which falls
upon the other portions. Evaporation, therefore, could not keep up the
supply. From whence, then, does it come? this twenty inches, thus lost by
the rivers and winds, and with such wonderful regularity every year.
"All the rivers run into the sea, yet the sea is not full. _Note the place
whence the rivers come, hither they return again._"
But how is it that they thus return with such wonderful regularity, in a
narrow traveling belt of daily rains within the tropics, and a movable
belt of irregular rains without the tropics, extending to the poles,
leaving a space on each side of the equator encircling the earth in like
manner (except at two points, _viz._, Eastern Asia and Eastern North
America), from which they do not go, and to which they do not return, and
which is almost entirely unfurnished with rain? And all this without any
relation, whatever, to the contiguity of the oceans? Obviously this is not
the work of mere evaporation, or of the accidental or irregular
commingling of winds with different dew points, or quantities of moisture
in solution, or accidental, irregular changes of barometric pressure. _It
is one vast, wonderful, connected, and regular system--co-extensive with
the globe--necessary to the return of moisture from the oceans upon the
most inconsiderable portion of it, and to the condensation of the local
moisture of evaporation; and by it the waters are returned from the oceans
as regularly and bountifully upon the far interior of the great continents
in the same latitudes, as upon the "isles which rest in their bosoms."_