[_Dark monsoon inshrouds_. l. 129. When from any peculiar situations of land in respect to sea the tropic becomes more heated, when the sun is vertical over it, than the line, the periodical winds called monsoons are produced, and these are attended by rainy seasons; for as the air at the tropic is now more heated than at the line it ascends by decrease of its specific gravity, and floods of air rush in both from the South West and North East, and these being one warmer than the other the rain is precipitated by their mixture as observed by Dr. Hutton. See additional notes, No. XXV. All late travellers have ascribed the rise of the Nile to the monsoons which deluge Nubia and Abyssinia with rain. The whirling of the ascending air was even seen by Mr. Bruce in Abyssinia; he says, "every morning a small cloud began to whirl round, and presently after the whole heavens became covered with clouds," by this vortex of ascending air the N.E. winds and the S.W. winds, which flow in to supply the place of the ascending column, became mixed more rapidly and deposited their rain in greater abundance. Mr. Volney observes that the time of the rising of the Nile commences about the 19th of June, and that Abyssinia and the adjacent parts of Africa are deluged with rain in May, June, and July, and produce a mass of water which is three months in draining off. The Abbe Le Pluche observes that as Sirius, or the dog-star, rose at the time of the commencement of the flood its rising was watched by the astronomers, and notice given of the approach of inundation by hanging the figure of Anubis, which was that of a man with a dog's head, upon all their temples. Histoire de Ciel.] [Illustration: Fertilization of Egypt.] [_Egypt's shower-less lands_. l. 138. There seem to be two situations which may be conceived to be exempted from rain falling upon them, one where the constant trade-winds meet beneath the line, for here two regions of warm air are mixed together, and thence do not seem to have any cause to precipitate their vapour; and the other is, where the winds are brought from colder climates and become warmer by their contact with the earth of a warmer one. Thus Lower Egypt is a flat country warmed by the sun more than the higher lands of one side of it, and than the Mediterranean on the other; and hence the winds which blow over it acquire greater warmth, which ever way they come, than they possessed before, and in consequence have a tendency to acquire and not to part with their vapour like the north-east winds of this country. There is said to be a narrow spot upon the coast of Peru where rain seldom occurs, at the same time according to Ulloa on the mountainous regions of the Andes beyond there is almost perpetual rain. For the wind blows uniformly upon this hot part of the coast of Peru, but no cause of devaporation occurs till it begins to ascend the mountainous Andes, and then its own expansion produces cold sufficient to condense its vapour.]