Use of the instruments — Forecasting weather from natural phenomena, etc.

WEATHER wisdom is more necessary to the man who travels along the coast in a small vessel than to any one else. A large vessel is constructed to encounter any weather with safety, and she must take fair and foul as she finds it; but the safety of a small craft often depends entirely on an accurate forecast of the wind. When the skipper of the little yacht undertakes a voyage, say from Harwich to Rotterdam, he has to pick his weather. He waits in port till he gets a slant — that is, until he has satisfied himself that in all human probability no wind of dangerous strength will blow in the course of the next few days — then he weighs his anchor, hoists his sails, and speeds across the broad sea as fast as he is able, knowing that should a gale of wind spring up before he has made the opposite coast, he will be in considerable peril and not improbably be lost.

But the mariner who has made himself acquainted with the science of meteorology can make a coasting voyage, even in a tiny craft, from one end of Europe to the other, sailing from port to port in favourable weather, and dodging the storms that would infallibly destroy him, by foreseeing them and remaining in snug harbours until they have passed by.

In following the rules which we shall now lay down, the amateur will sometimes find that his forecast of storm will prove a false alarm and will keep him in port idle while he might have been at sea; but on the other hand — and what is far more important — a forecast of fair weather is very rarely wrong; a really dangerous wind is scarcely ever known to spring up without having given a due warning of its approach.

If about to sail from any British port — for instance, across the Channel — in a small yacht, it is useful to remember that one can telegraph the Meteorological Office, London, for a weather forecast for that particular voyage. The reply — the charge for which is one shilling — will be returned by telegraph without delay.

Such a forecast is more to be relied on than the opinion of all the weather-wise old sailors on the coast.

The weather can be foretold with considerable accuracy by observing the appearance of many natural phenomena, the clouds, the water, the sun and moon, and also by the movements of fish and fowl; but the changes of the barometer are far more to be depended on than the above as indications of coming weather.

Every small yacht should be provided with an aneroid barometer, which is more sensitive and indicates change more quickly than the mercurial barometer, also with a thermometer, and, if the yachtsman wishes to have a complete meteorological outfit, with a hygrometer or wet-bulb thermometer. These three instruments will enable him to measure the weight, the temperature, and the degree of moistness of the atmosphere. The last of the instruments mentioned is often not found on a small yacht, and indeed the aneroid and thermometer suffice for ordinary purposes of weather-forecast.

It must be remembered, while foretelling the weather, that the barometer is affected —

Firstly, by the direction of the wind. The greatest rise being with the north-east wind.

Secondly, by moisture, an increase of which will cause a fall.

Thirdly, by the force of the wind. If a wind freshens, the moisture and direction of the wind remaining the same, the glass will fall.

These three causes do not often act in accord; one is generally affecting the glass in a way opposite to the other two. It is for this reason that an observation of the barometer alone will often mislead us. It must be read in conjunction with the thermometer and also with the hygrometer, in order to determine the the cause of the rise of fall of the mercury.

Admiral Fitzroy's two well-known rules are —

THE BAROMETER RISES for northerly wind (including from N.W. by the N. to E.), for dry or less wet weather, for less wind, or for more than one ofthese changes; except on a few occasions, when rain (or snow) comes from the north with strong wind.

THE BAROMETER FALLS for south wind (including from S.E. by the S. to W.), for wet weather, for stronger wind, or for more than one of these changes; except on a few occasions, when moderate wind with rain (or snow) comes from the northward.

The following rules are selected from the official computation, which is very comprehensive and should be studied by every yachtsman. Admiral Fitzroy's book should be on every yacht's library shelf.

If the barometer has been at its ordinary height — about thirty inches at sea-level — and is steady or rising, while the thermometer falls, and dampness lessens, N.W., N., or N.E., or less wind may be expected.

If the barometer is falling, the thermometer rising, and the dampness increasing, wind and rain, or snow may be expected from S.E., S., or S.W.

The most dangerous shifts of wind and the heaviest gales from N. happen after the mercury first rises from a very low point.

A rapid rise of the barometer indicates unsettled weather; a slow rise, or steadiness with dryness shows fair weather.

The greatest depressions of the barometer are with gales from S.E., S., or S.W.; the greatest elevations with winds from N.W., N., or N.E.

Sudden falls of the barometer with west wind are sometimes followed by violent storms from N.W. and N.

If a gale sets in from the E. or S.E., and the wind veers by the S., the barometer will continue falling until the wind becomes S.W., when a comparative lull may occur, after which the gale will be renewed, and the shifting of the wind towards the N.W. will be indicated by a fall of the thermometer as will as a rise of barometer.

If a change of weather is long foretold by the barometer, the longer the presaged weather will last, and vice versa. The sailor expresses this in the rhyme —

"Long foretold, long last;
      Short warning — soon past."

Many more rules have been laid down by the meteorological observers, for which we have no space here; but we will now give a few brief rules on the forecast of weather by the observation of natural phenomena, which are useful by themselves. but still more so when confirming the forecast we have made from the instruments.

A halo round the moon, especially if it appear distant and yet very distinct, indicates a gale of wind, and probably rain.

When high lands are shrouded in mists, south-west gales and rain may be expected.

If distant objects are very clear and raised by reflection, rain (possibly wind also) is near.

"Wind dogs," which are like broken portions of a rainbow seen to windward in the morning, are very certain signs of a gale.

"Mare's tails," which are ragged streaks of cloud, having little motion, foretell gales from the direction they radiate from.

In fine weather the wind generally follows the sun, that is, it blows from the east in the morning and from the west in the evening.

If the wind blows from west in the morning, and "backs" against the sun, that is, it blows from the east in the evening, bad weather will follow.

A red sunset presages fine weather.

A red sunrise presages bad weather.

A bright yellow sky at sunset is a sign of wind; a pale yellow, of wet.

A gloomy dark blue sky is a sign of wind, while a light blue sky indicates fine weather.

The sun's setting or rising behind a bank of clouds indicates rough weather.

A phosphorescent sea is a very certain sign of a continuance of fine weather.

The presence of vast quantities of jelly-fish presages fine weather.

Sea-birds fly far out to sea in fine weather; but if they fly inland bad weather may be expected.

When porpoises come into shallow water and ascend the rivers, stormy weather is near.

In conclusion, we will remind the yachtsman that the Meteorological Office issues a daily forecast of the weather for different portions of the British Isles. This forecast is now published in nearly all the leading morning papers, and should always be studied, if possible, before one starts across a broad sea in a little yacht; for it warns us of the "Yankee gale" that is on its way across the Atlantic, and whose approach has been announced by cable long before the barometer or the appearance of the sky gives us any sign.