Biela's comet was sought in vain, a series of strange discoveries had
been made respecting meteors, which led astronomers to believe that,
even though the missing comet might never again be seen as a comet,
we might still learn something respecting its present condition.
It had been noticed that the remarkable comet of 1862 (comet 11 of
that year) crossed the earth's track near the place where she is on
August 10-11, the time of the August meteors, called the Tears of St.
Lawrence in old times, but now known as the Perseids, because they seem
to radiate from the constellation Perseus. Later the idea occurred
to Schiaparelli, an Italian astronomer, that the August meteors may
travel along the path of that comet. He could not prove this, but he
advanced very strong evidence in favour of the opinion, for he found
that bodies travelling along the path of the comet of 1862 would seem
to radiate from Perseus as they traversed the earth's atmosphere. It
was as if a person suspected that a steam-cloud seen on a distant
railway track belonged to a particular train, and, though unable
actually to prove this, was yet able to show that, with the wind and
weather then prevailing, that train, travelling at its customary rate,
would leave a steam-cloud behind it precisely of the apparent length
and position of the observed steam-cloud. This cloud might have the
observed position though otherwise produced, yet the evidence would be
thought strongly to favour the supposition that it came from the train
in question. In like manner the August meteors might be travelling on
any one of a great number of tracks intersecting the earth's orbit in
the place occupied by the earth on August 10-11; yet it was at least a
striking coincidence that a flight of meteors travelling in the orbit
of the chief comet of 1862 would seem to radiate from the constellation
Perseus, precisely as the August meteors do.
While astronomers were still discussing the ideas of Schiaparelli,
Professor Newton of Yale College, in America, called their attention
to the great display of November meteors which might be expected on
November 13-14, 1866. The fine shower of that year was well observed,
and the part--we may almost say the point--of the constellation Leo
from which the meteors radiated was correctly determined. And now a
strange thing happened. Those who believed in Schiaparelli's account of
the August meteors supposed of necessity that the bodies forming that
system travel in an orbit of enormous extent, for the comet of 1862
travels on a path extending much further from the sun than the path of
Neptune. There was, therefore, nothing to prevent them from believing
that the Leonides travel in a track carrying them far away from the
sun. The recurrence of great displays of these meteors at intervals of
about 33 years might be readily explained on such an assumption, for if
the Leonides have a period of about 33 years, their path must extend
far beyond the path of Uranus. But hitherto astronomers had not been
ready to admit such an explanation of the periodic recurrence of great
displays of the November meteors. They preferred theories (for several
were available) which accounted for the 33-year period, while assigning
to the Leonides paths of much less extent. Now that the idea of vast
meteoric orbits had been fairly broached, some astronomers thought it
might at least be worth while to calculate the path of the November
meteors on the assumption that their true period is about 33-1/4 years.
This was perfectly easy, because the period of a body travelling round
the sun determines the velocity at any given distance from the sun,
and knowing thus (at least, on this assumption) the true velocity of
the Leonides as they rush into our air, while their apparent path is
known, their true course is as readily determined as the true course
of the wind can be determined by a seaman from the apparent direction
and velocity with which it reaches his ship. When the path of the
November meteors had been determined (on the assumption mentioned),
it was found to be identical with the path of a comet which had only
been discovered a few months before-the comet called Tempel's. That a
comet which is invisible to the naked eye should have been discovered
in the very year when first astronomers made exact observations of the
meteors which travel in its track--for it will presently be seen that
the assumption above mentioned was a just one--cannot but be regarded
as a very singular coincidence. It was a most fortunate coincidence
for astronomers, since there can be but little doubt that but for it
Schiaparelli's theory would very soon have been forgotten. As that
theory was itself suggested by the fortuitous recognition of another
comet (only visible at intervals of more than a century) at a time when
attention had been specially directed to the August meteors, it may
fairly be said that the theory which now associates meteors and comets
in the most unmistakable manner was suggested by one accident and
confirmed by another. Albeit such accidents happen only to the zealous
student of nature's secrets. We shall presently see that the fortunate
detection of Tempel's comet in 1866 was not the last of the series of
coincidences by which the theory of meteors was established.
Although the evidence favouring Schiaparelli's theory was now strong,
yet it was well that at this stage still more convincing evidence
was forthcoming. The date of the November display has changed since
the Leonides were first recognised, in such sort as to show that the
position of their path has changed. The change is due to the disturbing
attractions of the planets. It occurred to our great astronomer Adams,
discoverer with Leverrier of distant Neptune, to inquire whether the
observed change accorded with the calculated effects of planetary
attraction, if the Leonides are supposed to travel in any of the
smaller paths suggested by astronomers, or could be explained only by
the assumption that the meteors travel on the widely-extending path
corresponding to the 33-1/4 years period. The problem was worthy of
his powers--in other words, it was a problem of exceeding difficulty.
By solving it, Adams made that certain which Schiaparelli and his
followers had merely assumed. He showed beyond all possibility of
doubt or question that of all the paths by which the periodic meteoric
displays could be accounted for, the wide path carrying the November
meteors far beyond the track of Uranus was the only one which accorded
with the observed effects of planetary perturbation.
It was in the confidence resulting from this masterly achievement that
in 1872 some astronomers (among them Professor Alex. Herschel, one of
Sir J. Herschel's sons) announced the probable occurrence of a display
of meteors when the earth crossed the track of Biela's missing comet.
An occurrence of this sort was alone wanting to complete the evidence
for the meteoric theory. It had been found that the August Perseids
move as if they followed in the track of a known comet; the path of the
November Leonides had been shown to be identical with that of another
comet; if astronomers could predict the appearance of meteors at the
time when the earth should pass through the track of a known comet,
even those who could not appreciate the force of the mathematical
evidence for the new theory would be convinced by the meteoric display.
Possibly such observers would have been satisfied with a meteor shower
which would not have contented astronomers. The display must have
special characteristics to satisfy scientific observers. The path of a
body following Biela's comet being known, and its exact rate of motion,
the direction in which it must enter our earth's atmosphere (if at
all) is determined. Calculation showed this direction to be such that
every meteor would appear to travel directly from the constellation
Andromeda,--from a point near the feet of the Chained Lady. A meteor
might appear in any part of the sky, but its course must be directed
from that point, otherwise it could not possibly be travelling in the
track of Biela's comet.
The event corresponded exactly with the anticipations of astronomers.
On the evening of November 27, 1872, many thousands of small meteors
were seen. In England between 40,000 and 50,000 were counted. In Italy
the meteors were so numerous that at one time there seemed to be a
cloud of light around the region near the feet of Andromeda whence all
the meteor-tracks seemed to radiate. The meteors were unmistakably
travelling on the track of Biela's comet. They overtook the earth on
a path slanting downwards somewhat from the north--precisely in the
direction in which Biela's comet would itself have descended upon the
earth if at any time the earth had chanced to reach the part of her
path crossed by the comet's when the comet was passing that way.
Strangely enough, a German astronomer, Klinkerfues, seems to have
regarded the meteoric display of November 27, 1872, as an actual visit
from Biela's comet. He telegraphed to Pogson, Government Astronomer
at Madras, 'Biela touched earth on November 27, look out for it near
Theta Centauri;' which, being interpreted, means, Biela's comet then
grazed the earth, coming from the feet of Andromeda, look for it where
it is travelling onwards in the opposite direction--that is towards the
shoulder of the Centaur. As Biela's comet had in reality passed that
way twelve weeks earlier, the instructions of Klinkerfues were somewhat
wide of the mark. However, Pogson followed them, and near the spot
indicated he saw two faint cloud-like objects, slowly moving athwart
the heavens. These he supposed to be the two comets into which the
missing comet had divided. It so happens, strangely enough, that these
objects, though moving parallel to the track of the missing comets,
were neither those comets themselves, nor the meteor flight through
which the earth had passed a few hours before. They were probably
somewhat richer meteor clouds, fragments (like the cloud through which
our earth had passed) of this most mysterious of all known comets.
To-night, or perhaps to-morrow or next night (for the position of the
meteor flights is not certainly known) we shall probably see meteors
travelling in advance of the main body. For the earth passes during
the next three days across the orbit of Biela's comet, about as far
in front of the head as she passed behind the head in 1872. Now,
there is no known reason for supposing (on _à priori_ grounds) that
meteors get strewn behind a comet's nucleus more readily than in front
of it. The disturbing forces which would tend to delay some meteoric
attendants would be balanced by forces which would tend to hasten
others. As a matter of fact it would seem that the meteor flights
which follow a comet's nucleus are commonly denser than those which
precede the nucleus. Yet in 1865 many thousands of Leonides were seen
which were in advance of the main body forming the comet of 1866. In
1859, 1860, and 1861, many Perseids were seen, which were in advance
of the comet of 1862. So that we might fairly expect to see a great
number of Andromeds to-night (or on the following nights) even if we
had none but the probabilities thus suggested to guide us. But since
many were seen on November 27 last, when the head of the comet, now
some four months' journey from us, was a whole year's journey further
away, it seems probable that on the present occasion a display well
worth observing will be seen should fine weather prevail. It will be
specially interesting to astronomers, as showing how meteors are strewn
in front of a comet. How meteors are strewn behind a comet we already
know tolerably well from observations made on the Perseids since 1862
and on the Leonides since 1865.
_COLD WINTERS._
During the cold weather of last December (1878) we heard much about
old-fashioned winters. It was generally assumed that some thirty or
forty years ago the winters were colder than they now are. Some began
to speculate on the probability that we may be about to have a cycle
of cold winters, continuing perhaps for thirty or forty years, as the
cycle of mild winters is commonly supposed to have done. If any doubts
were expressed as to the greater severity of winter weather thirty
or forty years ago, evidence was forthcoming to show that at that
time our smaller rivers were commonly frozen over during the winter,
and the larger rivers always encumbered with masses of ice, and not
unfrequently frozen from source to estuary. Skating was spoken of as a
half-forgotten pastime in these days, as compared with what it was when
the seniors of our time were lads. Nor were dismal stories wanting of
villages snowed up for months, of men and women who had been lost amid
snowdrifts, and of other troubles such as we now associate rather with
Siberian than with British winters.
Turning over recently the volume of the 'Penny Magazine' for the year
1837, I came across a passage which shows that these ideas about
winter weather forty years ago were entertained forty years ago about
winter weather eighty or ninety years ago. It occurs in an article on
the 'Peculiarities of the Climate of Canada and the United States.'
Discussing the theory whether the clearing away of forests has any
influence in mitigating the severity of winter weather, the writer
of the article says, 'Many persons assert, and I believe with some
degree of accuracy, that the seasons in Europe, and in our own island
particularly, have undergone a remarkable change within the memory
of many persons now living; and if such really be the case, how few
attempts have been made to account for this change, since no great
natural phenomenon, like that of clearing away millions of acres of
forest timber, and thereby exposing the cold and moist soil to the
action of the sun's rays, has recently taken place here; so that if the
climate of Great Britain has actually undergone a change, the cause,
whatever that may be, must be of a different nature from that generally
supposed to affect the climate of North America.' It must be explained
that, though in this passage the writer does not speak of a diminution
in the severity of the winters, it is a change of that sort that he is
really referring to. He had said, a few lines before, that 'some of
the older inhabitants of North America will declare to you that the
winters are much less severe "now" than they were forty or fifty years
ago,' and in the passage quoted he is discussing the possibility of a
similar change in Europe, where, however, as he points out, the cause
assigned to the supposed change in America has certainly no existence.
Since 1830, by the way, the theory has been advanced that the supposed
mildness of recent winters may have been caused by the large increase
in the consumption of coal, owing to the use of steam machinery, gas
for lighting purposes, and so forth.
I believe it will be found on careful inquiry that the change for
which forty years ago men sought a cause in vain, and for which at
present they assign a perfectly inadequate cause, has had no real
existence. The study of meteorological records gives no valid support
to the theory of change. Nor is it difficult to understand how the idea
that there has been a change has arisen from the changed conditions
under which men in middle life, as compared with children, observe
or feel the effects of milder weather. A child gives no heed to mild
winters. They pass, like ordinary spring or autumn days, unnoted and
unremembered. But a bitter winter, or even a spell of bitter weather
such as is felt almost every year, is remembered. Even though it lasts
but for a short time, it produces as much effect on the childish
imagination as a long and bitter winter produces on the minds of grown
folk. Looking back at the days of childhood, the middle-aged man or
woman recalls what seems like a series of bitter winters, because
recalling many occasions when, during what seemed a long time, the snow
lay deep, the waters were frozen, and the outdoor air was shrewd and
biting.
Before considering some of the remarkable winters which during the last
century have been experienced in Great Britain and in Europe generally,
I would discuss briefly the evidence on which I base the belief that
the winter weather of Europe, and of Great Britain especially, has
undergone no noteworthy change during the last century.
If there is any validity in the theory at present in vogue that our
winters are milder now than they were forty or fifty years ago, and
the theory in vogue as we have seen forty years ago that the winters
then were milder than they had been forty or fifty years earlier, it is
manifest that there ought to be a very remarkable contrast between our
present winter weather and that which was commonly experienced eighty
or ninety years since. Now, it so chances that we possess a record of
the weather from 1768 to 1792, by a very competent observer--Gilbert
White of Selborne--which serves to show what weather prevailed
generally during that interval; while the same writer has described
at length, in his own happy and effective manner, some of the winters
which were specially remarkable for severity. Let us see whether the
winters during the last third of the eighteenth century were so much
more bitter or long-lasting than those now experienced as common ideas
on the subject would suggest.
In 1768, the year began with a fortnight's frost and snow. The cold was
very severe, as will presently be more particularly noted. Thereafter
wet and rainy weather prevailed to the end of February. The winter of
1768-69 was marked throughout by alternations of rain and frost; thus
from the middle of November to the end of 1768 there were 'alternate
rains and frosts;' in January and February, 1769, the weather was
'frosty and rainy, with gleams of fine weather in the intervals; then
to the middle of March, wind and rain.' The last half of November,
1769, was dry and frosty, December windy, with rain and intervals of
frost, and the first fortnight very foggy; the first fortnight of
January, 1770, frosty, but on the 14th and 15th all the snow melted
and to the end of February mild hazy weather prevailed; March was
frosty and bright. From the middle of October, 1770, to the end of the
year, there were almost incessant rains; then severe frosts till the
last week of January, 1771, after which rain and snow prevailed for a
fortnight, followed by spring weather till the end of February. March
and April were frosty. The spring of 1771 was so exceptionally severe
in the Isle of Skye that it was called the Black Spring; in the south
also it was severe. November, 1771, frost with intervals of fog and
rain; December, mild and bright weather with hoar frosts; January and
the first week of February, 1772, frost and snow; thence to the end of
the first fortnight in March, frost, sleet, rain, and snow.
The winter of 1772-73 would fairly compare with the mildest in recent
years, except for one fortnight of hard frost in February, 1773. For
from the end of September to December 22 there were rain and mild
weather--the first ice on December 23--but thence to the end of the
month foggy weather. The first week in January, frost, but the rest of
the month dark rainy weather; and after the fortnight of hard frost in
February, misty showery weather to the end of the first week in March,
and bright spring days till April.
There were four weeks of frost after the end of the first fortnight in
November, 1773, then rain to the end of the year, and rain and frost
alternately to the middle of March, 1774.
In 1774-1775 there seems to have been no winter at all worth
mentioning. From August 24 to the end of the third week in November
there was rain, with frequent intervals of sunny weather. Then to the
end of December, dark dripping fogs. January, February, and the first
half of March, 1775, rain almost every day; and to the end of the first
week in April, cold winds, with showers of rain and snow.
The end of the year 1775 was rainy, with intervals of hoar frost and
sunshine. Dark frosty weather prevailed during the first three weeks of
January, 1776, with much snow. Afterwards foggy weather and hoar frost.
The cold of January, 1776, was remarkable, and will presently be more
fully described.
November and December, 1776, were dry and frosty, with some days of
hard rain. Then to January 10, 1777, hard frost; to the 20th foggy
with frequent showers; and to February 18, hard dry frost with snow,
followed by heavy rains, with intervals of warm dry spring weather to
the end of May.
The winter of 1777-78 was another which resembled closely enough those
winters which many suppose to be peculiar to recent years. The autumn
weather to October 12 had been remarkably fine and warm. From then to
the end of the year, grey mild weather prevailed, with but little rain
and still less frost. During the first thirteen days of January there
was frost with a little snow; then rain to January 24, followed by six
days of hard frost. After this, harsh foggy weather with rain prevailed
till February 23; then five days of frost; a fortnight of dark harsh
weather; and spring weather to the end of the first fortnight in April.
The second fortnight of April, however, was cold, with snow and frost.
Similarly varied in character was the winter of 1778-79. From the end
of September, 1778, to the end of the year the weather was wet, with
considerable intervals of sunshine. January, 1779, was characterised by
alternations of frost and showers. After this, to April 21, warm dry
weather prevailed.
The winter of 1779-80 was rather more severe. During October and
November the weather was fine with intervals of rain. December rainy,
with frost and snow occasionally. January 1780, frosty. During February
dark harsh weather prevailed, with frequent intervals of frost. March
was characterised by warm, showery, spring weather.
November and December, 1781, were warm and rainy; and the same mild
open weather prevailed till February 4. Then followed eighteen days of
hard frost, after which to the end of March the weather was cold and
windy, with frost, snow, and rain. Thus the first two-thirds of the
winter of 1781-82 were exceptionally mild, while the last third was
cold and bleak.
In November, 1782, we find for the first time in these records an
instance of early and long-continued cold. 'November began with a hard
frost, and continued throughout, with alternate frost and thaw. The
first part of December frosty.' The latter half of December, however,
and the first sixteen days of January were mild, with much rain and
wind. Then came a week of hard frost, followed by stormy dripping
weather to the end of February. Thence to May 9, cold harsh winds
prevailed. On May 5 there was thick ice.
The next two winters were, on the whole, the severest of the entire
series recorded by Gilbert White, though at no time in the winter of
1783-84 was the cold greater than has often been experienced in this
country. White's record runs thus: From September 23 to November 12,
dry mild weather. To December 18, grey soft weather with a few showers.
Thence to February 19, 1784, hard frost, with two thaws, one on January
14, the other on February 5. To February 28, mild wet fogs. To March 3,
frost with ice. To March 10, sleet and snow. To April 2, snow with hard
frost.
The winter of 1784-85 was remarkable for the exceedingly severe
cold of December, 1784, which will presently be referred to more
particularly. From November 6 to the end of the year 1784, fog, rain,
and hard frost alternated, the frost continuing longest and being
severest in December. On January 2 a thaw began, and rainy weather with
wind continued to January 28. Thence to March 15 hard frost; to March
21 mild weather with sprinkling showers; to April 7 hard frost.
After rainy weather till December 23, 1786, came frost and snow till
January 7, 1787. Then a week of mild and very rainy weather, followed
by a week of heavy snow. From January 21 to February 11, mild weather
with frequent rains; to February 21 dry weather with high winds; and to
March 10, hard frost. Then alternate rains and frosts to April 13.
Early in November, 1786, there was frost, but thence to December 16
rain with only 'a few detached days of frost.' After a fortnight of
frost and snow, came 24 days of dark, moist, mild weather. Then four
days (from January 24 to January 28, 1787) of frost and snow; after
which mild showery weather to February 16, dry cool weather to February
28, stormy and rainy weather to March 10. The next fortnight bright and
frosty; then mild rainy weather to the end of April.
November, 1787, was mild till the 23rd, the last week frosty. The
first three weeks of December still and mild, with rain, the last week
frosty. The first thirteen days of January mild and wet; then five days
of frost, followed by dry, windy weather. February frosty, but with
frequent showers. The first half of March hard frost, the rest dark
harsh weather with much rain.