As to the formation of rain, it should be observed that absolutely pure air can not give either fog or drops of water when it is supersaturated with vapor. If there were no dust in the atmosphere we should have no clouds or rain. The sky would always be clear, and the sun would shine uninterruptedly as long as it was above the horizon. There would be no dawn or twilight, and day and night would succeed one another instantly, without transition. Atmospheric water would be deposited only when in contact with things, as in Aitken's experiments, very much as dew is deposited. The causes of the formation of rain are evidently the same everywhere. The secondary conditions change only according to climates; but they vary so much that rains are distributed very unequally over the earth. According to Desanis, the quantity of vapor contained in a column of air as high as the atmosphere would give, in France, a layer of water about four centimetres thick. Few rain storms would furnish so much; but there are storms sometimes that give much more. On August 17, 1888, seven centimetres of water fell at Clermont in five hours; and September 12, 1875, the pluviometer measured ten centimetres for the whole day. Still more copious rains fall in some tropical countries; at Purneah, in India, eighty-nine centimetres have fallen in twenty-four hours. Mr. John Murray has calculated, from the charts of Elias Loomis, that the quantity of rain falling every year over the whole earth would form a bed of water averaging nine hundred and seventy millimetres in depth. When we consider the annual quantities of rain in particular regions or localities, we find the numbers exceedingly variable, and some of them surprising. Clermont receives 630 millimetres, and the mean of the fall in Europe is about the same. About one metre falls on the western coast of Iceland, two metres in Norway, 2.80 metres in Scotland, 4.60 metres at Vera Cruz, 5.20 metres at Buitenzorg, in the Dutch East Indies, 7.10 metres at Maranhão, Brazil, and 12.50 metres at Cherrapunji, in British India. On the other hand, it rarely rains in some regions of the globe north and south of the equator; as in the center of the Sahara and of Arabia, the plateau of eastern Persia and Beluchistan, the desert of Kalahari, and the desert of Atacama. The plains or pampas of the eastern slopes of the Andes, in about 23° south latitude, are likewise subject to extreme droughts, in one of which, lasting three years, three million head of cattle perished.--_Translated for the Popular Science Monthly from Ciel et Terre._ FOOTNOTE: [12] An address before the Society of Horticulture and Viticulture at Clermont-Ferrand. DREAM AND REALITY. BY M. CAMILLE MELINAND.