Part 1

WEATHER WARNINGS FOR WATCHERS

BY THE “CLERK” HIMSELF.

WITH CONCISE TABLES FOR CALCULATING HEIGHTS

“The actuating force of every wind that blows; of every mighty current that streams through ocean depths; the motive cause of every particle of vapour in the air, of every mist and cloud and raindrop, is SOLAR RADIATION.”—_George Warington._

LONDON HOULSTON AND SONS

PATERNOSTER SQUARE, E.C.

1877

[_The right of translation is reserved. Entered at Stationers’ Hall._]

LIST OF WORKS OF REFERENCE.

BOUTAN ET D’ALMEIDA. Cours Eléméntaire de Physique.

BUCHAN, A. Introductory Text-book of Meteorology. _W. Blackwood and Sons_, 1871.

CAZIN, ACHILLE. La Chaleur. _Hachette and Co._, 1868.

CRAMPTON, REV. JOS., M.A. The Three Heavens. _W. Hunt and Co._, 1876.

CHAMBERS’ Encyclopædia. _W. and B. Chambers_, 1875.

DREW, JOHN. Practical Meteorology. _Van Voorst_, 1870.

FITZROY, THE LATE ADMIRAL. Weather Book and Barometer Manual.

FLAMMARION, CAMILLE. L’Atmosphere.

GUILLEMIN AMEDÉE. Les Forces de la Nature.

GLAISHER, J., F.R.S. Hygrometrical Tables. _Taylor and Francis_, 1869.

HARTLEY, W. N. Air and its Relations to Life. _Longmans_, 1875.

HERSCHEL, SIR JOHN F. W. Meteorology, from Ency. Brit. _A. and C. Black_, 1860.

KAEMTZ, L. F. Complete Course of Meteorology. _Baillière London._

MARTIN’S Natural Philosophy. _Simpkin, Marshall and Co._, 1868.

TYNDALL, JOHN, D.C.L., &c. Heat, a Mode of Motion. Fifth Edition. _Longmans_, 1875.

RODWELL. Dictionary of Science. _E. Moxon and Co._, 1871.

PROCTOR. Science Byways. _Smith, Elder and Co._, 1875.

SCOTT, R. H., M.A., F.R.S. Instructions in the Use of Meteorological Instruments, 1875.

WARINGTON, GEORGE. Phenomena of Radiation.

CONTENTS.

PAGE

Actinometer 10

Æthrioscope 16

Altitude tables 37

Anemograph 84

Anemometers, velocity 80

Aneroid barometer 35

Atmidometer 25

Atmospheric electricity 89

Barograph 38

Barometer precautions 40

„ description of 29

„ construction of 26

„ self-recording 36

„ warnings 43

„ syphon 30

„ wheel 33

„ corrections of 27

Beaufort’s scale of wind force 76

„ weather notation 82

Black bulb in vacuo 12

Boiling-point thermometer 36

Calorification 8

Condensation 45

Capacity, correction 27

Capillarity, correction 28

Centigrade thermometer 20

Cirro-cumulus cloud 56

Cirro-stratus cloud 56

Cirrus cloud 52

Clouds, forms of 52

„ amount of 57

Compass bearings 71

Conversion of thermometer scales 23

Cumulo-stratus cloud 56

Cumulus cloud 53

Dew-point 48

Electrification 86

Electrometers, forms of 90

Electroscope 89

Evaporation, measurement of 24

Fahrenheit’s thermometer 20

Fortin’s barometer 27

Freezing-point 20

Frost, management of hygrometer in 50

Gold-leaf electroscope 89

Glass, storm 41

Heights, measurement of 37

Hours of observation 39

Howard’s cloud nomenclature 52

Hygrometer, Daniell’s 47

Hygrometer, Mason’s 48

Hygrometer precautions 50

Kew verification 42

Lightning 90

„ conductors 91

Mean sea-level 28

Maximum thermometers 16

Meteorology, list of works on 4

Minimum thermometers 17

Mountain barometers 35

Motion 67

Nimbus clouds, form of 57

Ozone, determination of 91

Ozonometer 92

Packing barometers 32

Position of barometers 33

Pyrheliometer 9

Pressure anemometer 79

Psychrometer 49

Radiation, solar 9

Radio-solar thermometer 13

Rain, measurement of 60

Rain gauges 62 to 67

Rarefaction 26

Réaumur’s scale 20

Regnault’s hygrometer 47

Robinson’s anemometer 81

Solar radiation 9

Six’s thermometer 18

Standard barometer 28

Stevenson’s thermo-screen 51

Stratus cloud 55

Suspension of barometers 40

Sympiesometer 41

Temperature, correction for 27

Terrestrial radiation 13

Thermographs 23

Thermometer scales 20

„ screens 50

„ radiation 11, 14

„ standard 21

True bearings of wind direction 71

Vernier, principle of 30

„ setting the 31

Weather warnings 40, 44, 53, 54, 55, 56, 57, 58, 59, 60, 73, 77, 94

Wet and dry bulb hygrometer 50

Wind, registration of 85

„ gauges 79

„ scales 76, 83

„ vane 78

PREFACE.

The late Admiral Fitzroy entertained the opinion that the various phenomena which go to form what we call “weather” are “measurable at any place, and that having these measurements at _various_ places over a given area, such as the British Isles, we ought to be able to foresee the peculiar results as regards the direction and force of air currents which have their distinctive weather characteristics in relation to temperature, rainfall, and electrical manifestations.”

A conviction of the soundness of this opinion has induced the writer to make the present compilation, in the hope that many who have hitherto avoided the subject of meteorology and the weather may find interesting matter, where before all seemed dull and technical.

Any attempt at rigid mathematical accuracy is disclaimed at the outset; the leading principles involved in weather forecasting and storm prevision will, however, be stated in a sufficiently definite manner to divest the subject of the mystery in which it has hitherto seemed to be enshrined, and thus enable the unscientific reader to become weather-wise, and casual observers to note weather phenomena with some degree of method and precision.

On page 4 will be found a list of works which have proved useful aids in making the present compilation. The writer desires to acknowledge his indebtedness to the various authors and publishers, and especially to Mr. Strachan, for permission to quote from his able pamphlet on “Weather Forecasts, and Storm Prevision,” and to reproduce the valuable table on page 37, for Calculating Heights of Mountains, from the fourth edition of his handy “Pocket Meteorological Register.”

The publication of Weather Reports in the daily journals must have convinced the most indifferent that much greater importance is now attached to weather phenomena than formerly; and this conviction will be deepened when it is remembered that a Parliamentary grant of £10,000 is annually expended in support of the Meteorological Office and its seven fully organized observatories in this country, while America expends no less a sum than £80,000 annually in the pursuit of weather wisdom; and the leading nations of Europe have also established meteorological observatories in suitable localities.

The balloon ascents of Messrs. Glaisher and Coxwell attracted much attention to the instruments used in estimating atmospheric phenomena, and awakened a desire to know something of the functions of a barometer, thermometer, hygrometer, &c., and especially of the classification of those important weather-warners, clouds. These subjects will be found duly noted in their order, and every phenomenon being traced to its source, Solar Radiation, it is hoped that these pages may prove generally acceptable, and be deemed not altogether unworthy of

“THE CLERK OF THE WEATHER.”

WEATHER WARNINGS.

The two great Forces of Nature are Gravitation and Heat, which always act in opposition to each other.

WEATHER is the result of the action of these forces on matter, and where one form of force is in excess of another, changes are produced which become apparent to our senses, or are indicated by suitable instruments.

THE MATTER composing the earth on which we live is of three kinds—solid, liquid, and gaseous.

THE FORCE incessantly acting on these is the radiant heat of the sun.

THE RESULTS of this incessant action are:—

1. CALORIFICATION, or Heating, which, besides being appreciable by our senses, is indicated by the THERMOMETER.

2. EVAPORATION, which alters the weight of the air indirectly, by the diffusion of aqueous vapour through it. This alteration of _weight_ is indicated by the BAROMETER, the accompanying increase of moisture being indicated by the HYGROMETER.

3. RAREFACTION, which alters the _weight_ of the air directly.

4. CONDENSATION, producing fog, dew, rain, hail, and snow; all sufficiently apparent when they occur, but estimated accurately only by the Rain Gauge, or PLUVIOMETER.

5. MOTION, producing winds, which we are able to appreciate in the gentle breeze and the awful cyclone, the force and velocity of which are indicated by the ANEMOMETER.

6. ELECTRIFICATION, producing lightning, thunder, magnetic phenomena, and chemical change, respectively indicated by the ELECTROMETER, MAGNETOMETER, and OZONOMETER.

I.—CALORIFICATION.

Before considering in detail these results of the action of solar radiation on our globe, an attempt to realize the immensity of this stupendous force will materially aid in the general comprehension of the subject.

The earth is a sphere somewhat less than 8,000 miles in diameter; and if we assume, with the gifted author[1] of “The Phenomena of Radiation,”—“that it is about 91,300,000 miles from the sun, and moves around it in a slightly elliptical orbit, occupying rather more than 365 days; that its shape is globular, somewhat flattened at its two extremities; that it rotates upon its own axis in the space of 24 hours, that axis being inclined to the annual orbit at an angle of 23-1/2—if we further assume that solar radiation is of such kind and quantity as it is, we are enabled to account for the total amount of light and heat the earth receives, for the superior temperature and illumination of equatorial regions, as compared with polar, with the gradations of intermediate zones, for the alternation of day and night, and the annual progression of the seasons.

[Footnote 1: George Warington, F.C.S.]

“The actuating force of every wind that blows; of every mighty current that streams through ocean depths; the motive cause of every particle of vapour in the air of every mist and cloud and raindrop, is SOLAR RADIATION.

“The delicate tremor of the sun’s surface particles, shot hither through thirty million leagues of fine intangible æther, has power to raise whole oceans from their beds, and pour them down again upon the earth. We are apt to measure solar heat merely by the sensation it produces on our skin, and think it small and weak accordingly; a good coal fire will heat us more. But its true measure is the work it does. Judged by this standard, its immensity is overpowering. To take a single instance: the average fall of dew in England is about five inches annually; for the evaporation of the vapour necessary to produce this trifling depth of moisture, there is expended _daily_ an amount of heat equal to the combustion of sixty-eight tons of coal for _every square mile_ of surface, or, for the whole of England, 4,000,000 tons. Compare now the size of England with that of the whole earth—only 1/3388th part; extend the calculation to _rain_, as well as dew, the average fall of which on the whole earth is estimated at five feet annually, or _twelve_ times greater; and then estimate the sum of 4,000,000 × 3,388 × 12 = 162,624,000,000 tons, or about 3,000 times as much as is annually raised in the whole world; and we have the number of tons of coal required to produce the heat expended by the sun merely in raising vapour from the sea to give us rain during a single day.”

SOLAR RADIATION.

Seeing, then, that solar radiation plays so important a part in the production of the natural phenomena classed under the head of Meteorology, a description of the mode of estimating its amount will prove interesting, and enable the reader to realize the existence of this mighty power. M. Pouillet devised for this purpose the apparatus known as the PYRHELIOMETER, which registers the power of parallel solar rays by the amount of heat imparted to a disc of a given diameter in a given time. It consists of a flat circular vessel of steel A having its outside coated with lamp-black B. A short steel tube is attached to the side opposite to that covered with lamp-black, and the vessel is filled with mercury. A registering thermometer C, protected by a brass tube D, is then attached, and the whole is inverted and exposed to the sun, as shown at Fig. 1. The purpose of the second disc, E, is to aid in so placing the apparatus that it shall receive direct parallel rays. It is obvious that if the shadow of the upper disc completely covers the lower one, the sun’s rays must be perpendicular to its blackened surface.

“The surface on which the sun’s rays here fall is known; the quantity of mercury within the cylinder is also known; hence we can express the effect of the sun’s heat upon a given area by stating that it is competent, in five minutes, to raise so much mercury so many degrees in temperature.”[2]

[Footnote 2: Tyndall, “Heat a Mode of Motion.”]

Sir John Herschel also designed an instrument for observing the heating power of the sun’s rays in a given time, to which the title Actinometer is given. It consists of a Thermometer with a long open scale and a large cylindrical bulb, thus combining the best conditions for extreme sensibility. An observation is made by exposing the instrument in the shade for one minute and noting the temperature. It is then exposed to the sun’s rays for one minute, and a record of the temperature made. It is again placed in the shade for one minute, and the mean of the two shade readings being deducted from the solar reading shows the heating power of the sun’s rays for one minute of time.

The stimulus imparted to the study of this class of phenomena by the publications of Professor Tyndall’s researches on Radiant Heat has induced a demand among Meteorologists for instruments capable of yielding more available indications than those just described. This demand has been most efficiently supplied by the ingenuity of scientists and instrument makers.

The early form of Solar Radiation Thermometer was a self-registering maximum thermometer, with blackened bulb, having its graduated _stem_, only, enclosed in an outer tube. Errors arising from terrestrial radiation and the _variable_ cooling influences of aërial currents are all obviated in the improved and patented Solar Radiation Thermometer shown at Fig. 3, which consists of a self-registering maximum thermometer, having its _bulb and stem_ dull-blackened, in accordance with the suggestion of the Rev. F. W. Stow, and the _whole_ enclosed in an outer chamber of glass, from which the air has been completely exhausted. The perfection of the vacuum in the enclosing chamber is proved by the production of a pale white phosphorescent light, with faint stratification and transverse bands when tested by the spark from a Ruhmkorff coil. Due provision is made for this by the attachment of platinum wires to the lower side of the tube, and when tested by a syphon pressure gauge, the vacua have been proved to exist to within 1/50th of an inch of pressure. It will thus be seen that the indications are preserved from errors arising from atmospheric currents, and from the absorption of heat by aqueous or other vapours, the whole of the solar heat passing through the vacuum direct to the blackened bulb. The contained mercury expanding, carries the recording index to the highest point, and thus is obtained a registration of the maximum amount of solar radiation during the twenty-four hours. The great advantage accruing from the high degree of perfection to which this instrument has been brought is, _uniformity_ of construction, which renders the observations made at different stations _intercomparable_. An enlarged view of the thermometer is given at Fig. 3, showing the platinum wire terminations, whereby the vacuum is tested. The Rev. Fenwick W. Stow thus directs the manner in which the solar radiation thermometer should be used:—

1. Place the instrument four feet above the ground, in an open space, Fig. 4, with its bulb directed towards the S.E. It is necessary that the globular part of the external glass should not be placed in contact with or very near to any substance, but that the air should circulate round it freely. Thus placed, its readings will be affected only by direct sunshine and by the temperature of the air.

2. One of the most convenient ways of fixing the instrument will be to allow its stem to fit into and rest upon two wooden collars fastened across the ends of a narrow slip of board, which is nailed in its centre upon a post steadied by lateral supports (Fig. 4).

3. The maximum temperature of the air in shade should be taken by a thermometer placed on a stand in an open situation. Any stand which thoroughly screens it from the sun, and exposes it to a free circulation of air, will do for the purpose.

4. The difference between the maxima in sun and shade, thus taken, is a measure of the amount of solar radiation.

The remarkable phenomenon recently discovered by Mr. Crookes, in which light is apparently converted into motion, has, at the suggestion of Mr. Strachan, received an interesting application to meteorology. The arrangement is shown at Fig. 5, where a Solar Radiation Thermometer has a Crookes’ Radiometer attached to it, which, in addition to forming an efficient test as to the perfection of the vacuum, will, it is hoped, aid in eventually establishing a relation between intensity of radiation, as shown by the thermometer, and the number of revolutions of the radiometer. The instrument has so recently been devised that any positive statement as to its usefulness would be premature; it may, however, prove a valuable auxiliary to the solar thermometer, and eventually be so far improved as to become a more definite exponent of solar radiation than the thermometer.

TERRESTRIAL RADIATION.

It is an established fact, confirmed by careful experiments, that a mutual interchange of heat is constantly going on between all bodies freely exposed to view of each other, thus tending to establish a state of equilibrium. It has further been ascertained that, as the mean temperature of the earth remains unchanged, “it necessarily follows that it emits by radiation from and through the surface of its atmosphere, on an average, the exact amount of heat it receives from the sun.” This process commences _slowly_ at sunset, and proceeds with great rapidity at and after midnight, attaining its maximum effect in a long night, in perfect calm, under a cloudless sky, resulting in the condensation of vapour in the form of dew, or hoar-frost, when the temperature of the surface-air is reduced to the dew-point.[3]

[Footnote 3: See page 47.]