It is exceedingly desirable, in a practical point of view, to understand
the precise character of the reciprocal action which takes place between
the earth and the counter-trade, and produces the varied phenomena which
mark our climate. We have seen that the same laws, other things being
equal, operate every where, and that analogies may be sought in the
character of those phenomena elsewhere, under the same, or different,
modifying circumstances. Looking, therefore, at the magneto-electric
movable machinery as a whole, and its influence upon the atmospheric
circulation and conditions, we find many facts which point to a primary
action in the counter-trade, and others that point as significantly to a
primary local-inducing-action in the earth. Let us briefly review those to
which we have alluded, and advert to some others, and see what solution of
the question they will justify:
The belt of inter-tropical rains appears to be, in width, and amount of
precipitation, and annual travel north and south, proportionate to the
volume of trades which blow into it, the quantity of moisture they
contain, and the elevation of the surface over which they meet.
South America is the most thoroughly-watered country within the tropics,
except, perhaps, portions of Hindoostan, Burmah, Siam, etc., on
south-eastern Asia. The contrast between both, and Africa, as far as
explored, and as shown by its rivers, is most obvious. The Amazon, alone,
delivers more water to the ocean than all the rivers of Africa.
Of the width of the belt of rains over Africa, in the interior, we know
little. Its northern extension is less, by from 7 deg. to 10 deg., than the same
belt over South America, the West Indies, and Mexico. Probably its
southern is also. Upon South America, the southern edge is carried down to
Cochabamba, in latitude 18 deg., and probably to 25 deg., to the northern edge of
the coast-desert of Peru, while it is rarely, if ever, found over the
Atlantic below 7 deg., a difference of 12 deg. to 20 deg.. Over South America, too,
the quantity of water which falls is also vastly in excess of that which
falls upon the Atlantic. The main cause of these differences is obvious.
The N. E. counter-trades which blow over Africa, originate on a surface
which is rainless, as eastern Sahara, Egypt, Arabia, etc., or subject to a
dry season by the northern ascent of the southern line of the
extra-tropical belt, as the Barbary States, Syria, Persia, etc., and their
supply of moisture is necessarily scanty. On the south, the S. E. trades
originate, in part, upon the eastern portion of southern Africa, and, in
part, upon the Indian Ocean, and from the latter source, and a portion of
the Mediterranean, doubtless most of the water which falls upon Central
Africa, is derived.
The N. E. and S. E. trades which blow into the inter-tropical belt upon
the eastern portion of the Atlantic, originate upon similar surfaces, and
with like effect. Thus, the S. E. trades, in summer, are from the Southern
portion of Africa, and the N. E., in part, from the Mediterranean; and, in
winter, the N. E. from the deserts, Senegambia, Nigritia, etc., and the S.
E., owing to the narrowing of the African continent, mainly from the South
Atlantic and Indian Oceans. Going west, the belt widens, and its range
increases until the Andes are reached; but under their lee, on the western
side, a totally different state of things is found, and the belt of the
coast becomes broken and irregular, as we have seen in the citation from
Maury.
The width, extension, and excessive precipitation of the belt, over South
America, follow the same law. The South Atlantic widens out by the
trending of the coast to the S. W., and furnishes a large area for the
unobstructed formation and evaporative action of the S. E. trades. So the
trending of the coast to the N. W., from 5 deg. south to the northward, opens
a large area for a like formation and action of the N. E. trades. No
correspondingly favorable circumstances exist any where, except, perhaps,
around Hindoostan, and there the fall of rain is very excessive in some
places, as on the Kassaya hills, to the extent of 400 inches per annum. In
addition to this, the magnetic line of no variation, and of greater
intensity, which runs from our magnetic pole, obliquely, S. S. E., to its
opposite and corresponding pole in the southern hemisphere, enters the
Atlantic on the coast of North Carolina, and traverses it, and the eastern
portion of South America, through the whole trade-wind region. The
table-lands, and slopes, and high mountain peaks, meet the trades
successively, as they go west, and the latter wrench from them, to an
unusual extent, their moisture; depressing the line of perpetual snow, by
an increase of quantity on the eastern sides, several thousand feet, as it
is for a like cause depressed on the southern side of the Himmalayas. On
the eastern slopes and tops of the Andes, as we have seen, and owing to
their elevation, falls the moisture which, according to the working of the
machinery, and the law of curvature, should bless the coast line of Peru
and northern Chili, the eastern Pacific, northern Mexico, California,
Utah, and New Mexico; and, while the Andes stand, the curse of comparative
aridity must rest upon them all.
Southern Chili, and western Patagonia are supplied by the N. E. trades,
which originate in the West Indies, the Gulf of Mexico, and the Caribbean
Sea, and the Pacific, off Central America, in the neighborhood of the Bay
of Panama. But there, again, the same effect of elevation is seen. The
mountain slopes of southern Chili and Patagonia are abundantly supplied,
and their mountain ranges are drenched with rain, while eastern Patagonia
and southern Buenos Ayres, under their lee, are comparatively dry. So the
S. E. trades, which originate off the western coast of South America,
curve in upon, and aided by the oceanic currents, supply, abundantly, the
N. W. coast of this continent, north of California; and there, too, the
coast, and its elevated ranges, receive, as we have seen, a very large
proportionate supply of their moisture. Substantially, the same state of
things, as far as circumstances permit, is reproduced upon Malaysia,
Hindoostan, etc., and the interposition of arid New Holland upon the
evaporating trade-surface may be distinctly traced upon south-western
Asia. Deserts abound there; the Caspian Sea receives the drainage of a
very large surface, without an outlet; their southern line of
extra-tropical rains is carried up very far in summer, and their dry
season is intensely hot. (See an article in the American Journal of
Science, for July, 1846, by Azariah Smith.)
Another fact in this connection is worthy of a moment's consideration. The
magnetic equator, as sought by the dipping needle, is not coincident with
the geographical one. Humboldt found it, on the Andes, at 7 deg. 1' south, and
it has been found still lower in the Atlantic. Over Africa it rises above
the geographical equator, and descends again on the Indian Ocean. About
midway the Pacific, it becomes coincident with the equator of the earth
again. (See diagram, on page 83.) Perhaps it is not known, with certainty,
why this is so. The south pole may be situated nearer the geographical
pole than the north one--but this is not believed to be so, nor could it
make the difference. The greatest southern depression of the magnetic
equator is found where the lines of greatest intensity, and of no
variation, are found; and at the more intense of these lines exists the
greatest depression. From this, I think, it may be inferred that the
needle is affected by the greater magnetic intensity of the northern
hemisphere, to which it may yet appear the obliquity of the earth's axis
is owing. However this may be, or whatever the cause, no marked effect is
produced upon the trades. The S. E. trades, by reason of the greater
extent of ocean-surface on which they originate, are every where the most
extensive, regular, and forcible. The south polar waters, from which they
rise, are every where trenching upon, and overriding, the north polar
ones; and thus, by a most beneficent provision, the greater portion of the
habitable surface is placed in the northern hemisphere, and the principal
portion of the southern is left open to an extensive, active evaporative
action, which supplies the northern habitable surface with a large excess
of the needed moisture.
The condensation, and consequent precipitation, which takes place at the
passing of the trades, as we have already said, over the ocean and
lowlands, takes place mainly in the day-time. Upon the table-lands and
mountain-ranges, it often continues during the evening and night. The
morning, and early part of the day, however, in tropical countries, are
generally fair at all elevations.
Storms also originate in the equatorial belt, and issuing forth in great
volume and with great intensity of action, find their way up even within
the Arctic circle. Those which pass over this continent, or the northern
Atlantic, generally originate in the West Indies, some of them over the
Caribbean Sea, some over the islands, and some over the open ocean to the
east of them; and, nearly all the most violent, during the months of
August, September, and October. It would seem most probable that the
primary action in such cases was in the trades themselves, but it is by no
means certain that such is the case. This is the class of storms of which
Mr. Redfield has industriously investigated some twenty or more; Mr. Espy
some, and Lieutenant Porter two. Their course, when very violent, is often
more directly north than that of storms, however violent, which originate
north of the calms of Cancer, owing, perhaps, to their greater
paramagnetic character. This course I have myself observed, in several
instances, about the period of the autumnal equinox--never, however, more
southerly than from S. W. to N. E., on the parallel of 41 deg., except in
three, and, perhaps, four, instances, when it has been S. W. by S. to N.
E. by N. I know of no class of storms in relation to which the evidence of
primary action in the counter-trade is stronger than in those of the class
which originate on the ocean east of the Windward Islands. But it is not
satisfactory as to them. Doubtless the conflict of polarities between the
passing trades is sufficient to produce the showers and rains which are
ordinarily found over the ocean and lowlands, in the equatorial belt; but
it is doubtful whether it is sufficient to produce such extensive,
long-continued, and violent action, as that which characterizes the
hurricane autumnal gales.
They occur, too, at the time when the whole machinery of distribution has
reversed its course, and is rapidly pursuing its journey south. It is a
period of great magnetic disturbance, over both land and sea; of more
active gales and local-increased precipitation. At the Magnetic
Observatory of Toronto, Canada West, these disturbances are carefully and
systematically observed, and their maxima, or periods of greatest
disturbance occur in April and September. (See Silliman's Journal, new
series, vol. xvii. p. 145.)
The tendency to volcanic action is not as great at the autumnal, as at the
vernal equinox, for the reason that most of the volcanic action of the
western hemisphere develops itself now upon South rather than North
America. But both exist, and are active, and what are improperly termed
equinoctial storms, and gales, and rains, are proverbial during, or just
subsequent to, both periods with us--as they are when the same change,
called the breaking up of the monsoons, takes place in the line of
magnetic intensity, over southern and eastern Asia. A volume might be
filled with extracts, showing, at least, most remarkable coincidences
between violent volcanic action and great atmospheric disturbance. Perhaps
the increased fall of rain at and after the equinoxes, in the northern
hemisphere, and in certain localities subject to volcanic activity, is as
strikingly illustrated by the register, kept by Mr. Johnson, on the
volcanic Island of Kauai, one of the Hawaiian group, already alluded to,
as in any other case, although it is by no means a singular one. The
greatest fall of rain, in any month except April and October, was eight
inches. In April, the fall was fourteen inches, in October, eighteen
inches. Neither the equatorial, nor extra-tropical belt, were over the
island during those months; but they were the N. E. trades, and the result
was owing solely to the interposition of high volcanic mountains, _in a
state of disturbance_, into, or near, the strata of the counter-trade. Mr.
Dobson, in stating a theory to which we shall hereafter advert, advances
the following proposition:
"7. _Cyclones (hurricanes) begin in the immediate neighborhood of active
volcanoes._ The Mauritius cyclones begin near Java; the West Indian, near
the volcanic series of the Caribbean Islands; those of the Bay of Bengal,
near the volcanic islands on its eastern shores; the typhoons of the China
Sea, near the Philippine Islands, etc."
The peculiar stormy state of the atmosphere, over the Gulf Stream, to
which I have alluded, certainly affords no evidence of primary atmospheric
action. It is a body of south polar water, pursuing its way under the
guidance of magnetism--maintaining its polarity--arched somewhat like the
roof of a house, by the outward pressure of a cold north polar current
which it has met to the east of the Banks of Newfoundland, and forced to
take an in-shore course to the southward, and the bodies of water which
the rivers discharge, and a conflict with the north polar surface-winds
which sweep over it, and fogs, and thunder, and rain, are a matter of
course. Dr. Kane met a portion of this singular current in Baffin's Bay,
north of 75 deg., which had preserved its characteristics and a considerable
proportionate excess of heat, although it probably had been around
Greenland, or found its way to the west, toward the magnetic pole, through
some of its northern fiords or straits. (Grinnel Expedition, p. 120.)
The investigations of Lieutenant Maury show, that when the Gulf Stream
turns to the eastward, crossing the lines of declination at right angles,
as the counter-trades also seem to do in the same latitude, it is _carried
up, in summer, several degrees to the north_, and descends again in
winter--thus demonstrating its connection with the shifting magnetic
machinery which controls alike the ocean, the atmosphere, and the
temperature of the earth.[7]
There are other irregularities which deserve to be noticed, in this
connection, although the analogical evidence they afford is far from being
decisive.
I have already said that it was within my own observation, that
alternating lines of heat and cold, as well as rain and drought, existed
frequently, without regard to latitude, following, to some extent, the
course of the counter-trade. Such lines have been observed by others.
Thus, Mr. Espy, after describing a snow-storm, which was followed by a
very cold N. W. wind, of several days' continuance, says:
"This cold air covered the whole country, from Michigan to the
eastern coast of the United States, till the beginning of the great
storm of the 26th January; and, what is worthy of particular notice
is, that _the temperature began to increase first in the north and
north-west_. On the morning of the 25th, in the north-western parts
of Pennsylvania, and northern parts of New York, the _thermometer_
had already _risen in some places 30 deg._, and, in others, _above 40 deg._.
While in the S. E. corner of Pennsylvania, and in the S. E. corner of
New York it had not _begun to rise_. The _wind_ also began to change
from the _north-west_ to _south_ and _south-east_, _first_ in the
north-west parts of Pennsylvania and New York, some time before it
commenced in the south-east of those States; and, during the whole of
the 25th, the thermometer, in the north of New York, continued to
rise, though the wind was blowing from the southward, where the
thermometer was many degrees lower."
Thus, too, Mr. Redfield (American Journal of Science, November, 1846, p.
329):
"On the contrary, in times of the greatest depression of the
thermometer, in numerous instances, the cold period has been found to
have first taken effect in, or near, the tropical latitudes, and the
Gulf of Mexico, and has thence been propagated toward the eastern
portions of the United States, in a manner corresponding to the
observed progression of storms."
This was because the cold N. W. wind which _followed_ storms began to
follow them as the storms curved and passed to the N. E.
They occur in Europe also. Says Kaemtz:
"Such contrasts are not uncommon in Europe, and, in this respect, the
Alps form a remarkable limit; for they separate the climates of the
north of Europe from the Mediterranean climates, where the
distribution of rain is not the same as in the center of Europe.
Hence the differences between the climates of the north and south of
France. _If the winter is mild in the north_, the newspapers are
filled with the lamentations of the _Italians_ and _Provencals_ at
the _severity of the cold_."
These facts seem to indicate a primary action in the counter-trade.
Probably in connection with one class of storms they do, and with another
do not. I shall endeavor to show the distinction when I come to the
classification of storms.
The difference of seasons in this country, and over the entire northern
hemisphere, is often very great. In a remarkable work of a remarkable
man--"A Brief History of Epidemic and Pestilential Diseases," by Noah
Webster, published in 1799, 2 vols.--a history of the weather for about
two centuries--1600 to 1799 inclusive, is given generally, and then in a
tabular form. Those who think that every considerable extreme which occurs
exceeds any thing before known, will do well to consult that work.
Droughts are described, where "there was not a drop of rain for three or
four months, and cattle were fed upon the leaves of the trees." Winters,
so intensely cold that the thermometer fell to 20 deg. below zero, at
Brandywine; or so mild that there was little frost, and people upon
Connecticut River plowed their fields, and the _peach trees blossomed in
Pennsylvania in February_. These extremes generally existed in Europe and
America at the same time, but occasionally they were opposite and
alternate. Says Mr. Webster, in summing up the facts (vol. ii. p. 12): "It
is to be observed that in some cases a severe winter extends to both
hemispheres, sometimes to one only, and in a few cases to a part of a
hemisphere only. Thus in 1607-8, 1683-4, 1762-3, 1766-7, 1779-80, 1783-4,
the severity extended to both hemispheres. In 1640-41, 1739-40, and in
other instances, the severe winter in Europe preceded, by one year, a
similar winter in America. In a few instances, severe frost takes place in
one hemisphere during a series of mild winters in the others; but this is
less common. In general, the severity happens in both hemispheres at once,
or in two winters, in immediate succession; and, as far as this evidence
has yet appeared, this severity is closely attendant on volcanic
discharges, with very few exceptions."
It will be seen that Dr. Webster (LL.D. and not M.D., and therefore the
remarkable character of the work) attributes great influence to
earthquakes and volcanic action. Probably he is correct in this. The
present active volcanic action of the western hemisphere is nearly all
within the trade-wind region, from Mexico to Peru inclusive. The West
India islands are of volcanic origin, and the influence of volcanic action
is not confined to a concussion of the earth, or the eruption of mud and
lava. Its connection with magnetic action, and disturbance, is
unquestionable. But whether they operate to increase or diminish the
trades, and the extent to which they induce violent electric action and
storms within and without the tropics, is a question which further
observation must determine. The ripples of the ocean, compared by
Lieutenant Banvard to that of a "boiling cauldron, or such as is formed by
water being forced from under the gate of a mill-pond," are met with in
the vicinity of volcanic islands, where hurricanes and water-spouts
originate, and have been observed to precede storms, and be connected with
a falling barometer. But whether they are volcanic or magneto-electric,
it is difficult to determine. Dr. Webster remarks, as the result of
observation, during the 17th century, that earthquakes had a N. W. and S.
E. progression in the United States, and especially in New England. In a
recent article, Professor Dana has examined, with great ability, the
general and remarkable trending of coast lines, groups of islands, and
ranges of mountains, from N. E. to S. W. and from N. W. to S. E. (American
Journal of Science, May, 1847.)
The line of magnetic intensity, which connects our magnetic pole with its
opposite, is now upon this continent nearly a N. W. and S. E. line, and
the pole is fast traveling to the west. It may, and probably will yet, be
established, that there is an intimate connection between the cause of
volcanic action within the earth, to which the upheaval of the N. W. and
S. E., and N. E. and S. W. ranges were due, and of magnetic action
without, and between both, and the cause of _the S. E. extension_ of our
summer storms and belts of showers and barometric _waves_, and the
_peculiar N. W. wind_. Our limits do not permit us to pursue the subject.
Much influence upon the weather has been attributed to the spots upon the
sun. These spots are supposed to be breaks or openings in the luminous
atmosphere or photosphere of the sun, through which its dark nucleus body
is seen. Counselor Schwabe, of Dessau, has made them his study since 1826,
and has arrived at some singular results. They seem to be numerous--in
groups--and to appear periodically with minima and maxima of ten years.
As the result of his observations, from 1826 to 1850, he gives us the
following table and remarks:
+-----------------------------------------------+
| Year. | Groups. | Days showing | Days of |
| | | no spots. | Observation. |
|-------|---------|--------------|--------------|
| 1826 | 118 | 22 | 277 |
| 1827 | 161 | 2 | 273 |
| 1828 | 225 | 0 | 282 |
| 1829 | 199 | 0 | 244 |
| 1830 | 190 | 1 | 217 |
| 1831 | 149 | 3 | 239 |
| 1832 | 84 | 49 | 270 |
| 1833 | 33 | 139 | 267 |
| 1834 | 51 | 120 | 273 |
| 1835 | 173 | 18 | 244 |
| 1836 | 272 | 0 | 200 |
| 1837 | 333 | 0 | 168 |
| 1838 | 282 | 0 | 202 |
| 1839 | 162 | 0 | 205 |
| 1840 | 152 | 3 | 263 |
| 1841 | 102 | 15 | 283 |
| 1842 | 68 | 64 | 307 |
| 1843 | 34 | 149 | 312 |
| 1844 | 52 | 111 | 321 |
| 1845 | 114 | 29 | 332 |
| 1846 | 157 | 1 | 314 |
| 1847 | 257 | 0 | 276 |
| 1848 | 330 | 0 | 278 |
| 1849 | 238 | 0 | 285 |
| 1850 | 186 | 2 | 308 |
+-----------------------------------------------+
"I observed large spots, visible to the naked eye, in almost all the
years not characterized by the minimum; the largest appeared in 1828,
1829, 1831, 1836, 1837, 1838, 1839, 1847, 1848. I regard all spots,
whose diameter exceeds 50", as large, and it is only when of such a
size that they begin to be visible to even the keenest unaided sight.
"The spots are, undoubtedly, closely connected with the formation of
faculae, for I have often observed faculae, or narben, formed at the
same points from whence the spots had disappeared, while new solar
spots were also developed within the faculae. Every spot is surrounded
by a more or less bright, luminous cloud. I do not think that the
spots exert any influence on the annual temperature. I register the
height of the barometer and thermometer three times in the course of
each day, but the annual mean numbers deduced from their observations
have not hitherto indicated any appreciable connection between the
temperature and the number of the spots. Nor, indeed, would any
importance be due to the apparent indication of such a connection in
individual cases, unless the results were found to correspond with
others derived from many different parts of the earth. If the solar
spots exert any slight influence on our atmosphere, my tables would,
perhaps, rather tend to show that the years which exhibit _a larger
number of spots_ had a _smaller number of fine days_ than those
exhibiting few spots."
These observations _seem_ to show that the spots exert no influence upon
the weather, and to be satisfactory. But, perhaps, they are not entirely
so. No effect would, of course, be expected from day to day, and perhaps
the annual mean may not be seriously disturbed, and yet the spots may
seriously affect the seasons. Popular tradition has fixed upon certain
periods, of 10, 20, and 40 years, for the return of winters of unusual
severity; and the tables of Mr. Webster, and other facts, show that it is
not wholly without foundation. If we, and those we have cited, are not
mistaken in most of the views expressed, the natural effect of a partial
interception or failure of the sun's rays, by or from the existence of the
spots, would be to decrease the exciting power of the solar rays upon
terrestrial magnetism, and, as a consequence, the volume of the trades and
their amount of moisture. This would increase the _mean_ heat of the
summer in the temperate zone--for the _less_ the volume of trade, the less
precipitation and variable wind, and succeeding polar waves of cooler air,
and the greater mean heat. On the other hand, the same cause, and the
feebler heating power of the sun's rays, would make the winters more
severe, both from an absence of a portion of heat, derived directly from
the sun's rays, and a less mitigating influence, from the action of the
trade, by reason of its decreased volume. So, too, the absence of spots,
and a more powerful influence from the solar rays, may gradually carry
the machinery further north in summer, and further south in winter, and
thus make the _seasons extreme_ without seriously disturbing the mean of
the year. And both these may occur in a more marked degree over our
intense magnetic area than in Europe. I am satisfied that they do so
occur. That the partial failure of the sun's rays limits the transit of
the machinery, and the volume of the trades during the latter half of the
decade, and extends the transit and increases the volume during the first
half, producing an occasional severe summer drought and severe winter, in
the warmest portion of the decade. And that the variations correspond with
the difference in the character and number of the spots in different
decades, and hence the longer and shorter periods.
Turning to the tables of Dr. Webster, we find that a general tendency to
extreme seasons does seem to exist from the 6th to the 10th year of every
decade, and especially of every alternate decade. The periods of 1707-8,
1728, 1737 and 1739, 1749-50, 1758-9, 1779-80, 1798-9, are those in which
the tendency was seen most decided. These tables are very general. The
thermometer was not perfected till about 1700, and did not get into
general use before 1750. There were very few meteorological registers
kept, or accessible to Dr. Webster. Hence he was obliged to resort to such
other sources of information as were open to him, and such statements as
he found are not always entirely reliable. The oldest inhabitant is apt to
express himself very strongly respecting present extremes, and fail
somewhat in his recollection of those which have past. Still his tables
afford general and obvious evidence of the regularity of those periodic
conditions.
+---------------------------------------------------------+
|A. D.| Summer. | Winter. |
|-----|-------------------------|-------------------------|
| 1701| hot and dry | .... |
| 1702| hot and dry | .... |
| 1703| .... | .... |
| 1704| dry Europe | .... |
| 1705| .... | .... |
| 1706| hot, dry Europe | .... |
| 1707| very hot | .... |
| 1708| .... | very severe |
| 1709| .... | .... |
| 1710| .... | .... |
| 1711| .... | cold Europe |
| 1712| wet England | .... |
| 1713| wet England | mild |
| 1714| dry and hot | .... |
| 1715| dry | .... |
| 1716| very dry | severe |
| 1717| .... | severe |
| 1718| hot and wet | .... |
| 1719| .... | cold America |
| 1720| dry Europe | .... |
| 1721| .... | .... |
| 1722| cold, wet | .... |
| 1723| .... | cold |
| 1724| wet England | .... |
| 1725| wet England | .... |
| 1726| .... | .... |
| 1727| dry, hot Amer. | .... |
| 1728| hot Amer. | severe Europe |
| 1729| .... | .... |
| 1730| .... | very cold Eng. |
| 1731| .... | .... |
| 1732| .... | severe Amer. |
| 1733| dry Eng. | .... |
| 1734| .... | .... |
| 1735| wet | .... |
| 1736| wet | .... |
| 1737| .... | very severe Am. |
| 1738| .... | .... |
| 1739| wet England | very severe Eng. |
| 1740| .... | very severe Am. |
| 1741| .... | .... |
| 1742| .... | severe Syria |
| 1743| hot | .... |
| 1744| .... | .... |
| 1745| .... | .... |
| 1746| .... | .... |
| 1747| hot and dry | severe |
| 1748| dry | .... |
| 1749| very dry | .... |
| 1750| very hot | very severe |
| 1751| wet England | severe Amer. |
| 1752| very hot Amer. | .... |
| 1753| .... | severe |
| 1754| .... | mild Amer. |
| 1755| .... | severe Europe |
| 1756| .... | severe Syria |
| 1757| .... | .... |
| 1758| hot | .... |
| 1759| .... | severe |
| 1760| .... | .... |
| 1761| very dry Amer. | .... |
| 1762| very dry Amer. | severe |
| 1763| .... | .... |
| 1764| hot Europe | .... |
| 1765| hot Europe | severe Europe |
| 1766| hot and dry Eur. | very severe |
| 1767| .... | cold |
| 1768| hot | .... |
| 1769| hot | .... |
| 1770| wet England | .... |
| 1771| wet Am. & Eng. | cold Europe |
| 1772| hot America | Am., great snow |
| 1773| .... | .... |
| 1774| .... | severe Europe |
| 1775| .... | .... |
| 1776| hot | severe Europe |
| 1777| .... | .... |
| 1778| hot | mild |
| 1779| hot Eng. | very severe |
| 1780| .... | .... |
| 1781| .... | .... |
| 1782| dry Amer. | .... |
| 1783| hot | very severe |
| 1784| hot | .... |
| 1785| dry Europe | cold |
| 1786| cool | cold |
| 1787| cool | .... |
| 1788| rainy Amer. | cold |
| 1789| cool spring, hot summer | severe Eur., mild Amer. |
| 1790| .... | .... |
| 1791| very hot Am. | cold |
| 1792| .... | .... |
| 1793| hot, dry Am. | mild Amer. |
| 1794| .... | severe Europe |
| 1795| Amer., hot, rainy | .... |
| 1796| Autumn very Dry Am. | cold Amer. |
| 1797| cool Am. | severe Amer. |
| 1798| very hot } | { long & severe |
| 1799| very dry Am. } | { Amer. & Eur. |
+---------------------------------------------------------+
Still more definite evidence is found in the meteorological tables of Dr.
Holyoke and Dr. Hildreth, and an account, by Dr. Hildreth, of the seasons
when the Ohio River was closed or obstructed by ice, found in Silliman's
Journal, new series, vol. xiii. p. 238.
Thus, we have, from the tables of Dr. Holyoke, the following annual means,
from 1786 to 1825, inclusive. I have arranged them in periods of five
years. It will be seen that there are three peculiarities observable.
First, a marked difference between the first and second periods of the
decade, corresponding, generally, with the presence or absence of the
spots. Second, a difference in the mean of the decades which may well be
supposed to correspond with the difference in the number or size of the
spots since a like difference is observable in number and size, and the
time when they reached their maxima and minima, in the table of Schwabe.
And, third, there are occasional single cold years during the warm period,
and these correspond with what the tables of Dr. Webster show for both the
sixteenth and seventeenth centuries. In relation to this, it should be
remembered that volcanic action is a frequent and powerful disturber of
the regular action of terrestrial magnetism, and that the extremes, for
that reason, are frequently meridional or local and alternating; and to
that cause very great extremes, and marked exceptions, may be due,
notwithstanding the spots upon the sun may exert an influence in producing
hot summers and cold winters toward the close of each decade. Thus, to
select an instance to illustrate this and explain an anomaly: The coldest
season during the whole period, embraced in the following tables, is that
of 1812. This occurs during the decrease of spots, and the warm half of
the decade. Turning to the table of volcanic action, and of earthquakes,
found in the Report of the British Association for 1854, we find that year
was remarkable for earthquakes in the United States and South America. In
December, 1811, earthquakes commenced in the valley of the Mississippi,
Ohio, and Arkansas, felt also at places in Tennessee, Kentucky, Missouri,
Indiana, Virginia, North and South Carolina, Georgia, and Florida, though
not so severely east of the Alleghanies, _which continued until 1813_.
About the same time they commenced in Caraccas, and, in March, 1812,
became severe over the greater portion of the northern section of South
America, and in the Atlantic. No such general and continued succession of
earthquakes occurred during the other periods embraced in the tables, and
the mean of the following five years was very low, embracing the memorable
cold summer of 1816.
+---------------------------------------------------------------+
| Cold Period. | Warm Period. | Cold Period. | Warm Period. |
|---------------|---------------|---------------|---------------|
|1786 48 deg..53 |1791 48 deg..963|1796 48 deg..678|1801 50 deg..432|
|1787 47 deg..88 |1792 48 deg..44 |1797 48 deg..135|1802 50 deg..794|
|1788 47 deg..676|1793 50 deg..96 |1798 49 deg..471|1803 50 deg..24 |
|1789 47 deg..68 |1794 50 deg..768|1799 48 deg..291|1804 48 deg..328|
|1790 46 deg..53 |1795 50 deg..173|1800 49 deg..989|1805 50 deg..792|
|---------------|---------------|---------------|---------------|
|Mean of | | | |
|period 47 deg..659|Mean 49 deg..901|Mean 48 deg..910|Mean 50 deg..117|
|---------------|---------------|---------------|---------------|
|---------------|---------------|---------------|---------------|
|1806 47 deg..982|1811 50 deg..76 |1816 47 deg..113|1821 48 deg..15 |
|1807 48 deg..132|1812 45 deg..28 |1817 46 deg..277|1822 49 deg..81 |
|1808 49 deg..485|1813 47 deg..702|1818 48 deg..009|1823 47 deg..58 |
|1809 47 deg..92 |1814 48 deg..279|1819 50 deg..75 |1824 49 deg..25 |
|1810 49 deg..001|1815 47 deg..607|1820 48 deg..70 |1825 50 deg..99 |
|---------------|---------------|---------------|---------------|
|Mean 48 deg..505|Mean 47 deg..925|Mean 48 deg..169|Mean 49 deg..15 |
+---------------------------------------------------------------+
The tables of Dr. Hildreth, from 1826 to 1854, inclusive, furnish,
generally, evidence of a like character. There are, however, an anomaly or
two which will be observed. From 1826 to 1830, the mean is high during
the period when spots were at a maximum. But that maximum embraced a much
less number of spots than the two succeeding ones. A contrast appears in
the tables of Dr. Hildreth, during the early period, for Dr. Holyoke's
register, for 1827, puts it _below the mean_, but Dr. Hildreth's one of
the _highest of the half century_. In 1835 commenced a period when the
spots were much more numerous, and from 1835 to 1838, inclusive, the
seasons were correspondingly below the mean. From that period to 1844 a
gradual and slightly irregular rise took place, excepting the year 1843,
when another cold year intervened. The table of earthquakes, published by
the British Association, closes with 1842, and I have not access to any
others. The occurrence of such cold years, in the warm period, at
intervals during the two centuries previous, and in 1812, and onward, and
evidently owing to increased volcanic action beneath the western portion
of the northern hemisphere, justifies the belief that the low temperature
of 1843 was owing to the same cause. The following are the means from the
tables of Dr. Hildreth:
+----------------------------------------------------------------+
|1826 54 deg..00|1831 50 deg..87|1836 50 deg..03|1841 52 deg..18|1846 53 deg..64|
|1827 54 deg..92|1832 52 deg..42|1837 51 deg..57|1842 52 deg..83|1847 52 deg..00|
|1828 55 deg..22|1833 54 deg..56|1838 50 deg..62|1843 50 deg..77|1848 52 deg..50|
|1829 52 deg..38|1834 52 deg..40|1839 52 deg..54|1844 53 deg..25|1849 52 deg..09|
|1830 54 deg..93|1835 50 deg..65|1840 52 deg..35|1845 52 deg..73|1850 51 deg..48|
|------------|------------|------------|------------|------------|
|Mean 54 deg..29|Mean 52 deg..18|Mean 51 deg..52|Mean 52 deg..35|Mean 52 deg..32|
+----------------------------------------------------------------+
The observations of Dr. Holyoke were made at Salem, Massachusetts; those
of Dr. Hildreth at Marietta, Ohio.
The following, in relation to the freezing of the Ohio River, is evidence
of a different kind, but shows the same general correspondence, and
particularly _the mildness of the winters when there were few spots_, and
their severity from 1836 to 1838, inclusive, when the spots were most
numerous:
1829.--River open all winter--some floating ice.
1830.--River closed 27th January.
1831.--Floating ice--closed 23d January--opened 20th February.
1832.--Closed in December, which was a very cold month--opened January
8, and remained open all winter.
1833.--Open all winter.
1834.--Open all winter.
1835.--Closed January 6--opened the last of the month--cold.
1836.--Closed 28th January--opened 25th February.
1837.--Closed from 8th December to 8th February. Cold year.
1838.--Closed from 13th January to 13th March. Cold year.
1839.--Closed from 6th December to 13th January.
1840.--Closed 29th December--opened 15th January.
1841.--Closed 3d January--opened 8th do.
1842.--Open all winter.
1843.--Closed 28th November--opened 5th December--open all the rest of
the winter.
1844.--Open all winter.
1845.--Open all winter.
1846.--Closed 5th December--opened again a few days--closed again on the
26th. It is not stated how long it remained closed.
1847.--Open all winter.
1848.--Much floating ice, but not closed--heavy rains and floods.
1849.--Floating ice in January, but not closed.
1850.--Floating ice, but not closed.
1851.--Open all winter--a little ice.
(December in the above table, means December previous).
This is more reliable as to the winter season than the tables of annual
means--although the evidence they afford, making due allowance for the
exceptions, is very striking.
I shall return to this part of the subject again.
But there is other evidence of the influence of these spots. Their
connection with the irregular magnetic disturbance of the earth has been
distinctly traced. Colonel Sabine, President of the British Association,
in his opening address, September, 1852, after reviewing the recent
discoveries in magnetism, says:--
"It is not a little remarkable that this periodical magnetic
variation is found to be identical in period, and in epochs of maxima
and minima, with the periodical variation in the frequency and
magnitude of the _solar spots_, which M. Schwabe has established by
twenty-six years of unremitting labor. From a cosmical connection of
this nature, supposing it to be finally established, it would follow
that the decennial period, which we measure by our magnetic
instrument, is, in fact, a solar period, manifested to us, also, by
the alternately increasing and decreasing frequency and magnitude of
observations on the surface of the solar disc. May we not have in
these phenomena the indication of a cycle, or period of _secular
change in the magnetism of the sun_, affecting visibly his gaseous
atmosphere or photosphere, and sensibly modifying the magnetic
influence which he exercises on the surface of our earth?"--American
Journal of Science, new series, vol. xiv. p. 438.
I think it may fairly be inferred, that although these spots do not
occasion the "cold spells" and "hot spells," and other transient
peculiarities, they do materially affect the _mean_ temperature of the
year, and exert an obvious influence when at their maxima; and there is a
tendency to an increase of the heat and dryness of summer, and the
severity of winter, at the periods named, in our excessive climate, and a
well-established connection between the spots and magnetic disturbances
and variations.
Popular opinion has ever attributed to the moon a controlling effect upon
the changes of the weather. If it be dry, a storm is expected _when the
moon changes_; or if it be wet, dry weather. Such popular opinions are
usually entitled to respect, and founded in truth. But every attempt to
verify _this opinion_, by careful observation and registration, has
failed. Weather-tables and lunar phases, compared for nearly one hundred
years, show four hundred and ninety-one new or full moons attended by a
change of the weather, and five hundred and nine without. The celebrated
Olbers, after _fifty years of careful observation_ and comparison, decided
against it. So did the more celebrated Arago, at a more recent
date--summing up the result of his observations by saying--"Whatever the
progress of the sciences, never will observers, who are trustworthy and
careful of their reputation, venture to foretell the state of the
weather." Still, the moon may influence the weather, though she may not
effect changes at her syzygies or quadratures, and this subject should not
be too summarily dismissed. That the moon can not effect changes at the
periods named seems philosophically obvious. She changes, for the _whole
earth_, within the period of twenty-four hours; yet, how varied the state
of things on different portions of its surface. The equatorial belts of
trades, and drought, and rains, cover from fifty to sixty degrees of its
surface, and know nothing of lunar disturbance. The extra-tropical belt of
rains and variable weather moves up in its season, uncovering 10 deg., or
more, of latitude, and admitting the trades and a six months' drought over
it, as in California, regardless of the moon. Under the zone of
extra-tropical rains, even upon the eastern part of the continent of North
America, "dry spells" and "wet spells" exist side by side; the focus of
precipitation is now in one parallel, and now in another--_storms_ exist
_here_ and _fair weather there_, on the same continent at the same time;
and as the moon's rays in her northing pass round the northern hemisphere
during the twenty-four hours, they, doubtless, pass from ten to thirty or
more storms, of all characters and intensities, moving in opposition to
her orbit--and as many larger intervening areas of fair weather, not one
of which are indebted to her for their existence, or "take thought of her
coming."
The storm, which originates in the tropics, pursues its curving way now N.
W., then N. E., and again north, to the Arctic circle, and, perhaps,
around the magnetic pole, over gulf, and continent, and ocean, _occupying
one third the time of a lunation, and two changes, perhaps, in its
progress_, without any perceptible or conceivable influence from her. Yet
every inhabitant of mother-earth, influenced by _coincidences remembered_,
and uninfluenced by _exceptions forgotten_, looks up within his limited
horizon, and devoutly expects from the agency of some phase of the moon, a
change for the special benefit of his _dot_ upon the earth's surface. Upon
how many of these countless dots is the moon at a particular phase, or
relative distance from the sun, to change fair weather to foul, or foul to
fair? Upon none. The storms keep on their way;--the wet spells, and the
dry spells, the cold and the hot spells alternate in their time, and
though the moon turns toward them in passing, her dark face, her half
face, or her full orb (the gifts of the sun, which confer no power), they
do not heed her. They are originated, and are continued, by a more potent
agent. They are the work of an atmospheric mechanism, as _ceaseless_ in
its operation as _time_, as _regular_ as the _seasons_, _as extensive as
the globe_.
Indeed, it seems as if it was expressly designed by the Creator that the
moon should not interfere materially with this atmospheric machinery. She
is the nearest orb; her influence would be controlling and continuous;
would follow her monthly path from south to north, and with changes too
violent, and intervals too long; and would interfere with the regular
fundamental operation in the trade-wind region, where she is _vertical_.
Aside from the attraction of gravitation, therefore, she seems to have
been so created as to be incapable of exerting any influence. She is
without an atmosphere; the rays which she reflects are polarized, and
without chemical or magnetic power; and, if it be true that Melloni has
recently detected heat in them, by the use of a lens three feet in
diameter, which could not previously be effected, its quantity is
exceedingly small, and incapable of influence. Doubtless, the attraction
of her mass is felt upon the earth, as the tides attest; and upon the
atmosphere as well as the ocean. But the atmosphere is comparatively
_attenuated_, and exceedingly so at its upper surface. Her attraction,
therefore, although felt, is not influential. She seemed, to Dr. Howard,
to produce in her northing and southing, a lateral tide which the
barometer disclosed, but owing to the attenuated character of the
atmosphere, neither the sun nor moon create an easterly and westerly tide,
that is observable, except with the most delicate instruments. Sabine is
believed to have detected such a tide by the barometer, at St. Helena, of
one four thousandth of an inch. But even this _infinitesimal influence_
may prove an error upon further investigation. There is a diurnal
variation of the barometer, but it is not the result of her attraction,
for it is not later each day as are the tides, exists in the deepest mines
as well as upon the surface, and is demonstrably connected with the
_group_ of _diurnal_ changes produced by the action of the sun-light and
heat upon the earth's magnetism.
Can the lateral tide, if there be one, affect the weather? for in the
present state of science it seems entirely certain that the moon can exert
an influence in no other way.
If the received idea of many, perhaps most, meteorologists, on which all
wheel barometers are constructed, that a _high barometer_ necessarily
produces _fair weather_, and a _low one foul_, were true, she certainly
might do so. But that idea can not be sustained, and there is no known
certain influence exerted by the moon upon the weather, in relation to
which we have any reliable practical data.
Humboldt appears to have adopted the impression of Sir W. Herschell, that
the moon aids in the dispersion of the clouds. (Cosmos, vol. iv. p. 502.)
But the tendency to such dispersion is always rapid during the latter part
of the day and evening, when there is no storm approaching, and the full
moon renders their dissolution visible, and attracts attention to them.
The Greenwich observations, also, carefully examined by Professor Loomis,
fail to confirm the impression of Herschell and Humboldt, and those
eminent philosophers are doubtless in this mistaken.
From this general and somewhat desultory view of the general facts, which
bear analogically upon the question, no decisive inference can be drawn in
relation to the seat of the primary influence which produces the
atmospheric changes. The preponderance is in favor of the magnetic, or
magneto-electric, action of the earth. We must come back to our own
country and grapple with the question at home.