BAI2STAIX.] 



METEOROLOGY. 



1195 



rainfall at Paris, or of Essex in our own country.* At 

 the equator, the entire fall for the year is produced 

 during 80 days ; whilst, in this country, from 150 to 200 

 wet days give the period during which the quantity for 

 the year is afforded. 



A great variety of circumstances must be taken into 

 account in connection with the differences which various 

 parts of the earth exhibit in respect to rainfall ; and it 

 will be exceedingly difficult to predicate, according to 

 any known law, the amount which is due at any par- 

 ticular place. As in the case of the average annual 

 temperature, and for similar reasons, the moisture, 

 elevation, and isothermal characteristics are combined as 

 influencing causes. In Europe, for instance, we may 

 notice two extremes ; one presented by the west coast, 

 extending from Bergen, in Norway, to Gibraltar, in 

 Spain, on the whole of which a mild temperature, con- 

 siderable rainfall, and a large number of rainy days, are 

 indicative of the yearly average of climate ; whilst from 

 the North Cape, through St. Petersburg, to Hungary 

 and Turkey, the annual rainfall is only from one-third 

 to a-half of that common to the range of country just 

 referred to. The former region flanks the ocean and the 

 Gulf-stream, whilst the interior of Russia is entirely 

 protected from moist air. In Norway, again, we find 

 that whilst, at the coast (Bergen, see following table), no 

 less than 77 inches fall, yet, in the same latitude, but 

 about 150 miles more inland, the annual average is not 

 more than 21 inches diminishing still more, until, at 

 St. Petersburg, it arrives at a minimum. 



The average annual direction of the wind has a great 

 influence on the climate of all places. In the north of 

 Africa, across the Sahara, easterly winds prevail for 

 about nine months out of the year, and, together with the 

 great heat, parch every object of either animal or vege- 

 table life. Throughout the western part of the Old 

 World, an easterly wind produces precisely such effects on 

 a smaller scale ; for it diminishes the rainfall, lessens the 

 suspended moisture, and, in certain years, affects the 

 climate most seriously, and interferes, harmfully, with 

 many agricultural pursuits. In the West Indies, the 

 ii'irth of South America, and Hindostan, we find an 

 opposite extreme. Situated in the tropics, surrounded by 

 the ocean, traversed by large rivers, and crossed by moun- 

 tain chains whose summits are crowned with perpetual 

 snow, the air, in those regions, at the sea-level, is loaded 

 with aqueous vapour, maintained at a high temperature 

 by the excessive tropical heat. A sudden down-draught 

 of cold air, caused by periodical disturbances in the upper 

 regions, and the return of both polar currents, causes a 

 heavy fall of rain within a short period ; and thus the 

 thirsty earth is suddenly compensated for the constant 

 loss it had sustained by rapid evaporation. The transition 

 from an arid desert into a luxuriant verdure of vegeta- 

 tion is almost as sudden ; whilst the rivers, swollen by 

 the enormous and sudden accession of water, overflow 

 their banks, and, as with the Nile, which traverses an 

 almost rainless district, spread fertility on all sides, 

 even to a great extent beyond their natural boundaries. 



Our antipodes, in Southern Australia, New Zealand, 

 itc. , have a greater fall of rain, on an average, annually, 

 tliau we experience, north of the equator, in the same 

 latitude. This is chiefly owing to their insular position, 

 and their being situated in the midst of oceans extending 

 for thousands of miles in all directions. Yet the interior 

 of Australia, far removed from such ocean influences, is 

 in a condition very similar to that of Africa, being 

 generally a dry sandy desert ; and many places, as 

 Sydney, <fcc., are visited at certain seasons by the hot 

 winds arising from the north-west. These, occasionally, 

 indicate a temperature so high as 120 to 130 in the 

 shade, and destroy every vestige of vegetable life : in a 

 moment the wheat-fields and fruit trees are blasted, and 

 the human subject suffers acutely from the suffocating 

 atmosphere. These winds are the analogues of the 



Excessive rainfalls are sometimes, and in certain places, noticed in 

 England. Thus, on Spmltling-fcll (beight 943 feet), near Borrowdale, 

 Cumberland, the mean of four years gave no lest than 1G3 inches, and it 

 has been nearly 200 in some ycara ; whilst the total annual fall docs not 

 exceed, on an average, 31 Inches for the whole country. 



sirocco of the Sahara and northern districts of Africa ; 

 and, like it, are loaded with fine sand or dust, which is 

 deposited in prodigious quantities. In either case the 

 causes are precisely the same viz. , the drying of a large 

 body of air by its passing over extensive sandy regions ; 

 an increase of its temperature, owing to the radiation of 

 the solar heat from the underlying ground ; and the 

 absence of mountain-ranges which usually protect the 

 adjacent country, and cool the hot air passing over their 

 snow-covered peaks. 



Some portions of the earth are almost entirely un- 

 visited by rain : amongst which may be named the greater 

 part of Thibet and Tartary ; many parts of Central 

 India ; Arabia ; Egypt ; Central Africa ; part of Chili, 

 &c. ; and, in each case, absence of ocean influences is the 

 cause. As might be expected, both animal and vegetable 

 life suffer accordingly ; but, in numerous instances, abun- 

 dant dews compensate for this deficiency of rainfall ; or 

 the overflow of rivers fed from distant mountains, peri- 

 odically supplies the place of rain as in the case of the 

 Nile, already named ; the Amazon, Mississippi, Ganges, 

 Indus, the Australian rivers, &c. Some parts of our 

 colonies in South Australia and Victoria, suffer seriously 

 in the absence of such periodical inundations, most of 

 the rivers in that country becoming little better than 

 pools in the dry season ; the lakes even being almost 

 desiccated in summer. Before the setting-in of the 

 rainy season in many countries, the atmosphere, which 

 had, perhaps for weeks or months, been clear and quite 

 free from clouds, &c., gives an indication of the coming 

 change. The wind attains a settled direction, which is 

 invariable in each year for that season ; hurricanes and 

 fearful thuuder-storms suddenly come on, and are followed 

 by rains, during which as much as one inch per hour 

 falls at some places. It is a most providential circum- 

 stance that the advent of the rainy season is thus fore- 

 warned, and its periodicity so regular ; as the torrents of 

 water, soon generated, would speedily wash away the 

 products of a year's growth. In some parts of the West 

 Indies the heavy rains fall in October, November, and 

 December ; but, during August, the islands are generally 

 visited by fearful hurricanes, some of which have almost 

 ruined the colonists, by the universal havoc which has 

 been occasioned. These storms, occasionally, spread 

 over the two following months, as at Jamaica, which has 

 a wet guason from May to August, and in October and 

 November; August, September, and October being the- 

 hurricane season. 



Although in several degrees of more southerly latitude, 

 China participates in a climate resembling, respectively, 

 those of England, France, and Northern Italy ; and the 

 productions of that interesting country are also in many 

 cases similar. It is to some extent affected by the 

 Pacific Ocean washing it on the east coast, as Europe is, 

 on the west, by the Atlautic ; the circumstances being 

 similar in many respects the direction of the wind, 

 however, being varied. S'.ianghae, in31N. lat. , possesses 

 one of the finest climates in the world ; and although 

 extremes of temperature are met with throughout the 

 country, still the air is generally salubrious, and ex- 

 tremely healthy even for Europeans. At Canton the 

 heat of summer is very great, and the yearly average is 

 high, being 70; yet whilst in a latitude of 23 N., or 

 nearly 30 further south than London, fires are required 

 in the houses during winter, and snow and frost are 

 occasionally seen in the streets. 



North America presents some curious peculiarities of 

 climate, which are rarely paralleled in any other part of 

 the globe. Generally speaking, the annual average ia 

 about 10 or 15 lower, for the same latitudes, than in 

 Europe, and the ranges of temperature are very excessive. 

 In Canada the thermometer stands frequently at 20 

 below zero in winter, or 52 below freezing-point ; whilst 

 in summer, a heat of 100, or 105, is commonly ex- 

 perienced. Quebec, in lat. 47 D N., has an average mean, 

 in winter, of 14, and in summer, of C8 showing a very 

 excessive type of climate ; whilst so far south as Georgia 

 (lat. 32 N.), the extreme ranges are from 13 to 100. 

 Compared with those, we may observe, that in lat. 32 S., 



