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rest. Sometimes the lower surface swells into various large protuberances, bending uniformly
downward ; and sometimes one whole side of the cloud wül have an inclination
to the earth, and the extremity of it wül nearly touch the gi'ound. When the eye is
under the thunder-cloud, after it is grown lai-ge and well-formed, it is seen to sink lower,
and to dai'keii prodigiously ; at the same time that a number of small clouds (the origin
of which can never be perceived) are seen in a rapid motion, driving about in very uncertain
directions under it. Whüe these clouds are agitated with the most rapid motions,
the rain commonly falls in the greatest plenty ; and if the agitation be exceedingly great,
it commonly hails.
1414. Lightning. While the thunder-cloud is swelling, and extending its branches
over a lai’ge tract of country, the lightning is seen to dart from one part of it to another,
and often to illuminate its whole mass. When the cloud has acquired a sufficient
extent, the lightning strikes between the cloud and the earth, in two opposite places ; the
path of the lightning lying through the whole body of the cloud and its branches. The
longer this bghtning continues, the less dense does the cloud become, and the less dai-k
its appearance ; till at length it breaks in different places, and shows a clear sky. Tliose
thunder-clouds are said to be sometimes in a positive as well as a negative state of
electricity. The electricity continues longer of the same kind, in proportion as the
thunder-cloud is simple and uniform in its direction ; but when the lightning changes
its place, there commonly happens a change in the electricity of the atmosphere over
which the clouds passed. I t changes suddenly after a very violent flash of lightning ;
but gradually when the lightning is moderate, and the progress of the thunder-cloud
slow.
1415. Lightning is an electrical explosion or phenomenon. Flashes of lightning are
usually seen in broad and undefined masses ; wlien their path ap[>cars angular or zigzag,
they are reckoned most dangerous. They strike the highest and most pointed objects in
preference to others, as hills, trees, spires, masts of ships, &c. ; so all pointed conductors
receive and tiu-ow off the electric fluid more readüy than those that are terminated by
flat suifaccs. Lightning is observed to take and follow the readiest and best conductor ;
and the same is the case with electricity in the discharge of the Leyden phial ; whence it
is infen-ed, that in a thunder-stonn it would be safer to have one’s clothes wet than dry.
Lightning burns, dissolves metals, rends some bodies, sometimes strikes persons blind,
destroys animal life, deprives magnets of their virtue, or reverses their poles ; and all
these are well-known properties of electricity.
1416. With regard to places o f safety in times o f thunder and lightning. Dr. Franklin’s
advice is, to sit in the middle of a room, provided it be not under a metal lustre, suspended
by a chain, sitting on one chair, and laying the feet on another. I t is still better, he
says, to bring two or tliree mattresses or beds into the middle of the room, and, folding
them double, to place the chairs upon them ; for, as they are not so good conductors as
the walls, the lightning will not be so likely to pass through them. But the safest place
of all is in a hammock hung by silken cords, at an equal distance from all the sides of
the room. Dr. Priestley observes, that the place of most perfect safety must be the cellar,
and especially the middle of it ; for, when a person is lower than the surface of the earth,
the lightning must strike it before it can possibly reach him. In the fields, the place of
safety is within a few yards of a tree, but not quite near it. Bcccaria cautions persons
not always to trust too much to the neighbourhood of a higher or better conductor than
their own body, since he has repeatedly found that the lightning by no means descends
in one undirided track, bnt that bodies of various kinds conduct their share of it at
the same time, in proportion to their quantity and conducting power. I t is sometimes
stated ' that certain kinds of trees are never stnick by lightning ; there is , however, no
foundation for this idea.
S e c t . Ü. O f the Means o f Prognosticating the Weather,
1417. The study o f atmospherical changes has, in all ages, been more or less attended to
by men engaged in the culture of vegetables, or the pasturage of animals ; and we,
in this countiy, are sui*prised at the degree of perfection to which the ancients attained
in this knowledge ; but it ought to be recoUectcd, that the study of the weather in the
countries occupied by the ancients, as Egypt, Greece, Italy, and the continent of Europe,
is a very different thing from its study in an island situated like ours. It is easy to foretell
weather in countries where months pass away without rain or clouds, and where
some weeks together, at stated periods, are as certainly seasons of rain or snow. It may
be asserted with truth, that there is a greater variety of weather in London in one week,
than in Rome, Moscow, or St. Petersburgh in three months. It is not, therefore, entirely
a proof of our degeneracy, or the infiuence of our artificial mode of living, that we cannot
predict the weather with such certainty as the ancients ; but a circumstance rather to be
accounted for from the pcciúiaiitics of om* situation.
T IIE ATMOSPHERE. 445
1418. A variable climate, such as ours, admits of being studied, both generally and locally
; but it is a study which requires habits of observation and reflection, like all other
studies ; and, to be brought to any useful degree of perfection, it must be attended to not
as it commonly is, as a thing by chance, and which every body knows, or is fit for, but
as a serious undertaking. The weather may be foretold from natm*al data, artificial
data, and from precedent.
1419. 27te naium? c?a£a for this study are,— 1. The vegetable kingdom; many plants
shutting or opening their flowers, contracting or expanding theii* parts, &c. on approaching
changes in the humidity or temperature of the atmosphere: 2. The animal kingdom ;
most of those familiar to us exhibiting signs on approaching changes, of which those by
cattle and sheep are more especially remarkable; and hence shepherds are generally, of
all others, the most correct in then* estimate of weather: 3. The mineral k ingdom;
stones, earths, metals, salts, and water of particular sorts, often showing indications of
approaching changes : 4. Appearances of the atmosphere, the moon, the general character
of seasons, &c. The characters of clouds, the prevalence of particular winds, and other
signs, arc very commonly attended to.
1420. The influence o f the moon on the weather has, in all ages, been believed by the
generality of m ankind: the same opinion was embraced by the ancient astronomers; and
sevcrai eminent pliilosophcrs of later times have thought the opinion not unwortliy of
notice. Although the moon only acts (as far at least as we can ascertain) on the waters
of the ocean by producing tides, it is nevertheless higidy probable, according to the observations
of Lambert, Toaldo, and Cotte, that, in consequence of the lunai* infiuence,
great variations do take place in the atmosphere, and consequently in the weather. Tbe
following principles will show the grounds and reasons for tlieir embracing the received
notions on tliis interesting to p ic : —
1421. There are ten situatiims in the moon’s orbit when she must particularly exert her
influence on the atmosphere; and when, consequently, changes of the weather most
readily take place. These are,—
1st, The new, and 2d, Th e /u //m o o n , when she exerts her influence in conjunction
with, or ill opposition to, the sun.
3d and 4tli, The quadratures, or those aspects of the moon when she is 90° distant
from the s u n ; or when she is in the middle point of her orbit, between the points of
conjunction and opposition, namely, in the flrst and third quarters:
5th, The perigee, and 6th, The apogee, or those points of the moon’s orbit, in wliich
she is at the least and greatest distance from the earth.
7th and 8tli, The two passages of the moon over the equator, one of which Toaldo
calls the moon’s ascending, and the other the moon’s descending, equinox; or the two
lunistices, as De la Lande terms them.
9th, Tlie boreal lunisticc, when the moon approaches as near as she can in each lunation
(or period between one new moon and another) to our zenith (that point in the horizon
which is directly over our heads).
10th, Tlie a.ustral lunistice, when she is at the greatest distance from onr zenith; for
the action of the moon vai'ies greatly, according to her obliquity. With these ten points
Toaldo compared a table of forty-eight years’ obsei'vations ; the result is, that the probabilities,
that the weather will change at a certain period of the moon ai*e in the following
proportions :— New moon, 6 to 1. First quai-ter, 5 to 2. Full moon, 5 to 2.
Last quarter, 5 to 4. Perigee, 7 to 1. Apogee, 4 to 1. Ascending equinox, 13 to 4.
Northern lunistice, 11 to 4. Descending equinox, 11 to 4. Southern lunistice, 3 to 1.
1422. That the new moon will bring with it a change o f weather is in the doctrine of
chances as 6 to 1. Each situation of the moon alters that state of the atmosphere which
has been occasioned by the preceding one; and it seldom happens that any change in
the weather takes place without a change in the lunai* situations. These situations are
combined on account of the inequality of then* revolutions, and the greatest effect is
produced by the union of the syzigies, or the conjunction and opposition of a planet with
the sun, with the apsides, or points in the orbits of planets, in which they are at the
greatest and least distance from the sun or earth. The proportions of theu* powers to
produce variations arc as follow: — New moon coinciding with the perigee, 33 to 1.
Ditto, with tlie apogee, 7 to 1. Fu ll moon coinciding with the perigee, 10 to 1. Ditto,
witb the apogee, 8 to 1. The combination of these situations generally occasions stonns
and tempests: and this perturbing power will always have the greater effect, the nearer
these combined situations are to the moon’s passage over the equator, paiticularly in the
months of March and September. A t the new and full moons, in the months of March
and September, and even at the solstices, especially the winter solstice, the atmosphere
assumes a certain character, by which it is distinguished for three and sometimes six
months. The new moons which produce no change in the weather are those that happen
at a distance from the apsides. As it is perfectly true that each situation of the moon
alters that state of the atmosphere which has been produced by another, it is also