tolerably so for England, where the weather is more changeable, and at the same time more temperate, than in other parts of Europe. Nevertheless, it is only an indication of probable results; it contains nothing absolutely certain. It is now almost a century since our great English meteorologist, Howard, turned his attention to the amount of rain which falls in a given locality and at a given season. Speaking of England, some have said that April is the driest month, and October the wettest; but Fitz-Roy says March and July. Howard showed, long ago, that the quantity of rain which falls in London in one year is very variable: In 1802 he found 14 inches; in 1810, 27; and in 1816, 32 inches. = Symons puts the mean rainfall per annum for London at 25 inches, and for all England at 31 inches. The proportion for the various seasons is roughly stated as: Winter 58; Spring 48; Summer 67; Autumn 74; total 24.8 inches. But averages (or means) are only useful for comparison. Engineers require to know the extremes; for these are what are actually experienced, and what we have to deal with in practice. stance, more rain may fall in an hour than is due to one month, according to averages. If the flow of water in our rivers during a dry season is taken as unity (one volume), the volume in wet weather is generally 300, and in extreme cases 500. A river in England may rise, from floods caused by rain, as much as 23 vertical feet; and in South Africa, and America, For in CHAPTER XXIII. - Fogs and Electricity - Ronayne's Discovery Luminous FogsPrevention of Thunderstorms and Hail. THOUSANDS of tons of water are evaporated daily from the waters of the ocean by the heat of the sun's rays; this water rises as vapour into the air, forms clouds, fogs, and dew; falls again as rain, produces springs, streams, and rivers, which flow to the sea, and whilst protecting the surface of the Earth from the effects of undue radiation, gives to the soil that degree of moisture which is essential to life and fertility. Fogs, in the days of Sir Humphry Davy, were thought to be always due to the cooling of the air lying over water; and, no doubt, a mist is often formed from this cause; but that is not invariably the case. George Harvey, in 1823, contradicted Davy's statement, and showed that fogs were sometimes formed when the temperature of the air on the land is higher than that of the water and the air above it, in which the fog exists. As early as 1814-five years before Davy's observation-Thomas Young showed, on the occasion of a remarkable fog which lasted from 27th December 1813 to 23rd January 1814, in London, the tempera |