rain that falls in the same latitude, on the different sides of the same continent, and particularly of the same island. The mean fall of rain at Edinburgh, on the eastern coast, is 26 inches; while at Glasgow, on the western coast, in nearly the same latitude, it is 40 inches. At North Shields, on the eastern coast, it is 25 inches; while at Coniston, in Lancashire, in nearly the same latitude, on the western coast, it is 85 inches.
The amount of rain in a district may be changed by destroying or forming forests, and by the inclosure and drainage of land. By thinning off the wood in the neighbourhood of Marseilles, there has been a striking decrease of rain in fifty years.
In Mr. Howard’s observations on the climate of this country, he has found, on an average of years, that it rains every other day; that more rain falls in the night than in the day; that the greatest quantity of rain falls in autumn, and the least in winter; that the quantity which falls in autumn is nearly double that in spring; that most rain falls in October and least in February, and that May comes nearest to the mean: that one year in every five, in this country, may be expected to be extremely dry, and one in ten extremely wet.
According to Dalton, the mean annual amount of rain and dew for England and Wales is 36 inches. The mean all over the globe is stated to be 34 inches.
There seems to be some real connexion between the changes of the moon and the weather. Mr. Daniell says, “No observation is more general; and on no occasion, perhaps, is the almanac so frequently consulted as in forming conjectures upon the state of the weather. The common remark, however, goes no further than that changes from wet to dry, and from dry to wet, generally happen at the changes of the moon. When to this result of universal experience we add the philosophical reasons for the existence of tides in the aërial ocean, we cannot doubt that such a connexion exists. The subject, however, is involved in much obscurity.” At Viviers, it was observed that the number of rainy days was greatest at the first quarter, and least at the last. Mr. Howard has observed that, in this country, when the moon has south declination, there falls but a moderate quantity of rain, and that the quantity increases till she has attained the greatest northern declination. He thinks there is “evidence of a great tidal wave,
or swell in the atmosphere, caused by the moon’s attraction, preceding her in her approach to us, and following slowly as she departs from these latitudes.”
Most dry climates are subject to periodical droughts. In Australia, they return after every ten or twelve years, and are then followed by excessive rains, which gradually become less and less till another drought is the consequence.
When Mr. Darwin was in South America, he passed through a district which had long been suffering from dry weather. The first rain that had fallen during that year was on the 17th of May, when it rained lightly for about five hours. “With this shower,” he says, “the farmers, who plant corn near the sea-coast, where the atmosphere is more humid, would break up the ground; with a second, put the seed in; and, if a third should fall, they would reap in the spring a good harvest. It was interesting to watch the effect of this trifling amount of moisture. Twelve hours afterwards the ground appeared as dry as ever; yet, after an interval of ten days, all the hills were faintly tinged with green patches; the grass being sparingly scattered in hair-like fibres a full inch in
length. Before this shower every part of the surface was bare as on a high road.”
A fortnight after this shower had fallen, Mr. Darwin took an excursion to a part of the country to which the shower had not extended. “We had, therefore,” he says, “in the first part of our journey a most faint tinge of green, which soon faded away. Even where brightest, it was scarcely sufficient to remind one of the fresh turf and budding flowers during the spring of other countries. While travelling through these deserts, one feels like a prisoner, shut up in a gloomy courtyard, longing to see something green, and to smell a moist atmosphere.”