determined the identity of lightning with the electrical discharge from
a machine, much attention has been devoted, not only to that form of
atmospheric electricity which displays itself in the thunder-cloud, but
to the electric condition of the air in all states of the weather.
These researches have established the fact that the air is always in an
electrical condition, even when the sky is clear and free from
thunder-clouds. The instruments employed for ascertaining the kind and
intensity of atmospheric electricity are called Electroscopes. Fig. 65
shows a modification of Saussure’s Electroscope, the basis of which is
a narrow-mouthed flint glass bottle with a divided scale to indicate
the degree of divergence of the gold leaves or straws. To protect the
lower part from rain, it is covered by a metallic shield about five
inches in diameter. Bohnenberger’s Electroscope indicates the presence
and quality of _feeble_ electric currents. Peltier’s Electrometer
yields the same result by the deflection of a magnetic needle. This
latter has been in use at Brussels for thirty years, and at Utrecht for
twenty years, and is highly recommended.
[Illustration: 65.
Electroscope.
Scale about 1/7.]
Singer’s Atmospheric Electroscope is an efficient form of the
instrument in which an ordinary gold-leaf electrometer has attached to
its circular brass plate a brass rod two feet in length, with a clip at
its upper extremity to receive a lighted paper or cigar fusee. The
electricity of the air in immediate contact with the flame, causes, by
induction, electricity of the opposite nature to accumulate at the
upper extremity, where it is constantly carried off by the convection
currents in the flame, leaving the conductor charged with the same kind
and power of electricity as that contained in the air at the time of
the experiment. The principle of this method was initiated by Volta,
and has been extended and applied by Sir William Thomson in his
Water-dropping Collector, which consists of an insulated cistern from
which water escapes through a jet so fine that it breaks into drops
immediately after leaving the nozzle of the tube. The result of this is
that in half a minute from the starting of the stream the can is found
to be electrified to the same extent as the air at the point of the
tube. The scale value of each instrument has to be separately
determined by repeated comparative experiments, and involves much
delicacy of manipulation.
It is chiefly important for the ordinary observer to know that the
occurrence of thunder and lightning should be always noted in the
column headed “Remarks.”
[Illustration: 66.
Lightning
Conductor.
Scale about 1/10.]
The destructive effects of lightning are too well known to need
description here; the means, however, by which these may be averted
demand a brief notice. Lightning when discharged from a cloud will
always choose the better of any two conductors which may present
themselves. The _stone_ of a church steeple and the _wood_ of a ship’s
mast are bad conductors, but a galvanized iron wire rope is the best
possible conductor, and accordingly this material is now generally
employed for the purpose. A lightning conductor consists of three
parts: 1, the rod, which extends beyond the summit of the building, 2,
the conductor, which connects the rod with the underground portion, and
3, the part underground. The connection between each of these must be
absolutely perfect, or the conductor will be faulty. The top is usually
of solid copper tipped with platinum (Fig. 66), the body of galvanized
iron rope, so as to adapt itself to the inequalities of the building
and yet have no sharp turns in it, while the part underground is of
solid iron rod. This latter portion should extend straight underground
for two feet, and being bent at right angles away from the wall, should
rest in a horizontal drain 10 to 15 feet long filled with charcoal, and
be again bent downwards into a well of water. Should water not be
available, it should rest in the centre of a hole 15 feet deep and 10
inches in diameter, tightly packed with charcoal, which, while
conducting the electricity from the rod into the earth, serves also to
preserve the iron from rusting.
OZONE.
The atmosphere, besides holding the vapour of water diffused throughout
its mass, contains also minute traces of carbonic acid and ammonia, and
a very remarkable substance called Ozone. Oxygen, one of the component
gases of the atmosphere, is capable of existing in two conditions; one
in which it is comparatively passive, and another in which it possesses
exceptional chemical activity, dependent apparently upon its electrical
condition, and in which state it possesses a peculiar smell which has
caused it to be named ozone.[16] The characteristic odour is always
observable near a powerful electric machine when it is being worked,
near a battery used for the decomposition of water, and in the air
after the passage of a flash of lightning. Its presence is most marked
near the sea-coast, and in localities remarkable for their salubrity;
and on account of its influence on health, it has been proposed by
Schonbein and others to include ozonometrical observations with the
ordinary meteorological observations.
[Footnote 16: Greek _ozo_, I smell.]
Although in minute quantities it is favourable to health, when existing
in undue proportion it irritates the mucous membrane of the nose and
throat, producing painful sores. It attacks india-rubber, bleaches
indigo, and oxidizes silver and mercury, differing in all these points
from ordinary atmospheric oxygen.
The chemical energy it possesses (which exceeds that of ordinary oxygen
as much as the latter exceeds atmospheric air as an oxidizing agent)
affords the means of ascertaining its presence and quantity. It
liberates iodine from its combination with potassium, and free iodine
colours starch a deep blue.
Schonbein, the discoverer of ozone, found that when strips of paper
previously saturated with starch and iodide of potassium and dried were
exposed freely to the air but protected from rain and the direct action
of the sun, they underwent a peculiar discoloration (when immersed in
water) after an exposure of 24 hours. A scale of tints numbered from
one to ten afforded the means of comparative observation, and thus the
Ozonometer was constructed, and a means established of registering the
amount of ozone in the air of various localities from day to day.
Schonbein also observed that the proportion of ozone was largely
augmented after heavy falls of snow. For the exposure of the ozone
papers, an ozone cage is employed, as shown at Fig. 67.
[Illustration: 67.
Ozone Cage.
Scale about 1/6.]
Ozone may be prepared artificially as a disinfectant by cautiously
mixing without friction or concussion equal parts of peroxide of
manganese, permanganate of potash, and oxalic acid. For a room
containing 1,000 cubic feet, two teaspoonfuls of the powder, placed in
a dish and moistened with water occasionally, will develop the ozone
and disinfect the surrounding air without producing cough.
The most important and interesting series of facts, however, connected
with ozone are those established by the researches of M. Houzeau, who
states:—
1. That country air contains an odorous oxidizing substance,
with the power of bleaching blue litmus, without previously
reddening it, of destroying bad smells, and of bluing iodized
red litmus.
2. That this substance is ozone.
3. That the amount of ozone in the air at different times and
places is variable, but this is at most 1/700,000 of its
volume, or 1 volume of ozone in 700,000 of air.
4. That ozone is found much more frequently in the country than
in towns.
5. That ozone is in greatest quantity in spring, less in
summer, diminishes in autumn, and is least in winter.
6. It is most frequently detected on rainy days, and during
great atmospheric disturbances.
7. That atmospheric electricity is apparently the great
generator of ozone.
The subject is one of great interest in its bearings on health, and
opens a wide field of scientific research, as may be inferred from the
opinion expressed by the Vienna Congress, which is that “the existing
methods of determining the amount of ozone in the atmosphere are
insufficient, and the Congress therefore recommends investigations for
the discovery of better methods.”
Mr. Lowe has published the valuable weather warnings tabulated on page
94, which are interesting as showing from a given number of
observations the value of each phenomenon:—
+------------------------------------------+--------------+-------------+
| | No. of | Followed in |
| | observations.| 24 hours by |
| +--------------+------+------+
| DEW. | | Fine.| Rain.|
| Dew profuse | 241 | 196 | 43 |
| Dew from 1st April to 30th Sept. | 185 | 161 | 24 |
| Dew from 1st Oct. to 30th March | 56 | 37 | 19 |
| CLOUDS. | | | |
| White stratus in the valley | 229 | 201 | 28 |
| Coloured clouds at sunset | 35 | 26 | 9 |
| SUN. | | | |
| Solar halos | 204 | 133 | 71 |
| Sun red and shorn of rays | 34 | 31 | 3 |
| Mock suns | 35 | 19 | 6 |
| Sun shone through thin cirro-stratus | 13 | 6 | 7 |
| Sun pale and sparkling | 51 | 27 | 24 |
| FROST. | | | |
| White frost | 73 | 59 | 14 |
| MOON. | | | |
| Lunar halos | 102 | 51 | 51 |
| Mock moons | 9 | 7 | 2 |
| Lunar burr | 64 | 47 | 17 |
| Moon shining dimly | 18 | 12 | 6 |
| Moon rose of a red colour | 8 | 7 | 1 |
| STARS. | | | |
| Falling stars abundant | 85 | 65 | 20 |
| Stars bright | 83 | 64 | 19 |
| Stars dim | 54 | 32 | 22 |
| Stars scintillated | 14 | 12 | 2 |
| AURORA. | | | |
| Aurora borealis | 76 | 49 | 27 |
| ANIMALS. | | | |
| Bats flying about in the evening | 61 | 45 | 16 |
| Toads in the evening | 17 | 12 | 5 |
| Landrails clamorous | 14 | 13 | 1 |
| Ducks and geese noisy | 10 | 7 | 3 |
| Spiders hanging on webs in the evening | 8 | 5 | 3 |
| Fish rise in the lake | 15 | 9 | 6 |
| SMOKE. | | | |
| Smoke rising perpendicularly | 6 | 5 | 1 |
+------------------------------------------+--------------+------+------+
Among the animals whose movements give weather warnings few are more
trustworthy than the leech. The reader may verify this by placing one
in a broad glass bottle, tied over with perforated leather, or bladder.
If placed in a northern aspect, the leech will be found to behave in
the following manner:—
1. On the approach of fine or frosty weather, according to the season,
it will be found curled up at the bottom. 2. On the approach of rain,
snow, or wind, it will rise excitedly to the surface. 3. Thunder will
cause it to be much agitated, and to leave the water entirely.
PERIODS.—M. Köppen states, as the result of his examination into the
chances of a change of weather, that _the weather has a decided
tendency to preserve its character_. Thus, at Brussels, if it has
rained for nine or ten days successively, the _next_ day will be wet
also in four cases out of five; and the chance of a change decreases
with the length of time for which the weather _from_ which the change
is to take place has lasted.
In the case of temperature for five-day periods, the same principle
holds good;[17] for if a cold five-day period sets in after warm
weather, we can bet two to one that the next such period will be cold
too; but if the cold has lasted for two months, we can bet nearly eight
to one that the first five days of the next month will be cold too. The
chance of change is, however, greater for the five-day periods than for
single days. Similar results follow for the months, but here again the
chance of change shows an increase.
[Footnote 17: “Recent Progress in Weather Knowledge,”
by R. H. Scott, F.R.S.]
“If we revert to the instance first cited, that of rain, the result is,
_not_ that if it once begins to rain the chances are in favour of its
never ceasing; all that is implied is, that the chances are against its
ceasing on a definite day, and that they increase with the length of
time the rain has lasted. The problem is similar to that of human life:
the chance of a baby one year old living another year is less than that
of a man of thirty.
“The practical meaning of all this is, that although we know that a
compensating anomaly for all extraordinary weather exists somewhere on
the earth’s surface, _e.g._, the very common case of intense cold in
America, while we have a mild winter in Britain, there is no reason as
yet ascertained to anticipate that this compensation will occur at any
given place during the year. In other words, when definite conditions
of weather have thoroughly established themselves, it is only with
great difficulty that the courses of the atmospheric currents are
changed.”
To bring within the limits of a popular pamphlet a notice of the
various phenomena classed under the head of Meteorology, it has been
necessary to exercise the utmost brevity. Brief, however, as the
treatment has been, reference has been made to the sciences of Heat,
Light, Electricity, Magnetism, Gravitation, Astronomy, Chemistry,
Geography, and Geology, thus corroborating the testimony of Sir John
Herschel, who states that “it can hardly be impressed forcibly enough
on the attention of the student of nature that there is scarcely any
natural phenomenon which can be fully and completely explained in all
its circumstances without a union of several—perhaps of all—the
sciences; and it cannot be doubted that whatever walk of science he may
determine to pursue, impossible as it is for a finite capacity to
explore all with any chance of success, he will find it illuminated in
proportion to the light which he is enabled to throw upon it from
surrounding regions. But, independently of this advantage, the glimpse
which may thus be obtained of the harmony of Creation, of the unity of
its plan, of the theory of the material universe, is one of the most
exalted objects of contemplation which can be presented to the
faculties of a rational being. In such a general survey he perceives
that science is a whole whose source is lost in infinity, and which
nothing but the imperfection of our nature obliges us to divide. He
feels his nothingness in his attempts to grasp it, and he bows with
humility and adoration before that Supreme Intelligence who alone can
comprehend it, and who ‘in the beginning saw everything that He had
made, and behold it was very good.’”
J. AND W. RIDER, PRINTERS, LONDON.
------------------------------------------------------------------------
Transcriber’s note:
Footnotes moved to end of paragraph.
All scale values in illustration captions retained. The value may
not be visually correct.
All fractions regularised to numerator/denominator.
Page 3, ‘Reaumur’s’ changed to ‘Réaumur’s,’ “Réaumur’s scale”
Page 9, closing single quote changed to double quote.
Page 12, full stop appended to illustration caption, “Scale about
1/20.”
Page 16, full stop appended to illustration caption, “9.”
Page 17, semicolon changed to full stop, “...it has never been
frozen.”
Page 23, first footnote changed from “8 R = 18 F.” to “8 R = 50 F.”
Page 27, ‘vice versâ’ changed to ‘vice versa,’ “...proportion, and
vice versa,...”
Page 30, dash changed to space, “29·500 inches.”
Page 34, ‘Hook’ changed to ‘Hooke,’ “...invented by Dr. Hooke.”
Page 37, ‘Aneriod’ changed to ‘Aneroid,’ “...by means of Barometer
or Aneroid,...”
Page 39, space changed to stop, “...between nine and ten p.m.”
Page 42, space inserted between ‘no’ and ‘less,’ “...at no less
than 212 miles.”
Page 46, illustration number added to caption, “38. Damp Detector.”
Page 51, comma moved to after ‘weather,’ “In cold calm weather,...”
Page 57, ‘!’ changed to ‘,’ “cloud reflector,”
Page 58, ‘2.’ changed to ‘2nd.,’ “...and 2nd. Velocity of Motion.,”
Page 74, degrees changed to minutes, “57° 29´ N.”
Page 79, ‘Guage’ changed to ‘Gauge,’ “Lind’s Anemometer or Wind
Gauge...”
Page 83, powers changed from subscripts to superscripts, “V^2.”
Page 87, reference in text to Fig. 65 changed to Fig. 64, “...and
Fig. 64 an arrangement...”
Page 94, full stops added after ‘STARS’ and ‘ANIMALS.’
End of Project Gutenberg's Weather Warnings for Watchers, by The Clerk