METEOROLOGY. 



as tall pillars of cloud stretching from the sea to 

 the sky, whirling round their axes, and exhibiting 

 the progressive movement of the whole mass pre- 

 cisely as in the case of the dust whirlwind. The 

 sea at the base of the whirling vortex is thrown 

 into the most violent commotion, resembling the 

 surface of water in rapid ebullition. It is a 

 popular fallacy that the water of the sea is sucked 

 up in a solid mass by waterspouts, it being only 

 the spray from the broken waves which is carried 

 up. 



What are sometimes called waterspouts on land 

 are quite distinct from these phenomena. They 

 are merely heavy falls of rain of a very local 

 character, and may or may not be accompanied 

 with whirling winds. 



Weather-forecasts. From the direct bearing 

 weather-changes have on human interests, they 

 have from the earliest times been closely watched, 

 so that the causes by which they are brought about 

 being discovered, their approach might be pre- 

 dicted with some degree of confidence. The crav- 

 ing in the popular mind for this knowledge is 

 strongly attested by the prognostics of the weather 

 current in every language, which, amid much that 

 is shrewd and of considerable practical value, 

 embrace more that is vague, and not a little that 

 is positively absurd. 



It may be laid down as a well established truth, 

 that no prediction of the weather can be made, in 

 the British Islands at least, for more than three, 

 or perhaps only two days beforehand. Yet a belief 

 in the prognostications of almanac-makers was 

 once nearly universal, and is still prevalent. 



The Moon and the Weather. The belief is 

 almost universal, that the weather is influenced 

 by the phases of the moon. A change of the 

 weather, either from foul to fair, or from fair to 

 foul, may be specially looked for, it is thought, 

 at the times of new and full moon, or even at the 

 quarters, though these last are not considered so 

 influential. This belief is found to be altogether 

 without foundation. 



The only predictions of the weather to be relied 

 on are of the kind described in speaking of storms, 

 where the telegraph comes into play. Almost all 

 the weather-changes of Europe begin from the 

 south-west, and pass over Great Britain to the 

 north-east. Unsettled or bad weather is accom- 

 panied with a low barometer ; elsewhere, the 

 barometer is higher. Thus, then, suppose that, 

 from weather-telegrams received, it is seen that 

 everywhere in Europe barometers are high, we 

 may be sure that no storm need be dreaded for 

 two days at least. But if, on the following morn- 

 ing, barometers begin to fall a little in the west 

 of Ireland, and an easterly wind begins to blow 

 generally over Great Britain and Norway, and a 

 south-east wind over France ; then, since the 

 winds blow towards the lowest barometer, or 

 rather a little towards the right of it, the presump- 

 tion is that a storm of greater or less severity is 

 coming up, the centre of which is likely to pass 

 over England. This ought, therefore, to be closely 

 watched by the telegraph, and the indications 

 announced from time to time. 



It is our proximity to the Atlantic that makes 

 it impossible to predict the weather beyond three 

 days at the utmost. In Norway and the Baltic, 

 and places towards the east of Europe, the weather 

 may be predicted for a longer time, since each 



storm as it appears in the west may be followed 

 in its course by the telegraph, and the places 

 which it threatens be warned of the coming 

 danger. In America also, where storms chiefly 

 advance from west to east, gales and unsettled 

 weather are predicted at the sea-board in the east 

 some days before. 



But the collecting of this information by the 

 telegraph is a work which, owing to the expense, 

 governments only can accomplish ; and from its 

 importance, it is an incumbent duty which they 

 should discharge for the benefit of the seafaring 

 population. 



From all that precedes, it will be clear enough 

 that the mere height of the barometer, at a partic- 

 ular place, taken by itself, affords no sure indica- 

 tion of what weather is coming ; so that the terms 

 Rain, Fair, Set Fair, marked on the common 

 weather-glass, are delusive. The quantity of 

 vapour in the air, the temperature, and the direc- 

 tion of the wind, are all to be taken into account. 

 And with regard to the barometer itself, it is not 

 so much the actual height that is of consequence, 

 as whether it is rising or falling, and whether the 

 rise or fall has been of long duration. A slow 

 rise continued for some days gives promise of 

 settled weather ; a steady and long-continued fall 

 indicates that a tract of unsettled and stormy 

 weather may be expected. A sudden and great 

 fall of the barometer is the sure forerunner of a 

 violent storm. 



CLIMATE. 



The climate of a place depends on its distance 

 from the equator, its height above the sea-level, 

 its position in reference to oceans, seas, and con- 

 tinents, the form of its surface, and the character 

 of its soil. The points to be stated in reference 

 to climate are, the mean temperature, the extreme 

 winter and summer temperatures, the range of 

 temperature daily, and from day to day, the 

 humidity, the total fall of rain, the frequency of 

 the falls, the relation of the amount fallen to the 

 ordinary amount of vapour in the air, the pre- 

 vailing winds, and the degree of variability of the 

 weather. In general, the southern hemisphere of 

 the globe is colder than the northern. 



The causes which determine most of these ele- 

 ments of climate have been already described ; 

 and the general results over the globe, as regards 

 the most important element, temperature, are 

 exhibited in the isothermal charts (page 42). 



Under the geography of Great Britain and 

 other countries, the peculiarities of their several 

 climates will be noticed. 



ELECTRICITY OF THE ATMOSPHERE. 



Thunder and Lightning Aurora Borcalis. 



The electric phenomena of the atmosphere 

 possess great interest, but are as yet imperfectly 

 understood (see ELECTRICITY). The discharges 

 of the excitement are well known under the terms 

 thunder and lightning, and they generally accom- 

 pany storms and hurricanes, but rather as effects 

 than causes. 



The aurora borealis, one of the most beautii 

 of meteoric phenomena, is now believed to be 

 connected with the magnetism of the earth. 



