পাতা:পদার্থবিদ্যাসার.djvu/৫১

40 roots and seeds of plants, and we should suffer great inconvenience from it. * 'Pup. Wliat benefit do we derive from therain ? Tut. It makes the earth fruitful, it refreshes the withering plants, it cools the air in the sumiaur. it supplies our springs, and forms our rivers, so that we are scarcely over in want of water. - Pup. Are there amy signs of approaching rain? Tut. Many; we call foresee its approach by the wind, by hirds, plants, &c. Pup. Witat depth of rain is supposed so fall upon the surface of the earth annually Tut. About thirty-four inches. Pup. What quaniity of wat 1 is sapposed to be evaporated off the earth's surface annually Tut. About sooty-one culic inches. Pup. ; low is the rainbow forio:ed? Tut. By the reflection of the rays of the sum up. on the drops of falling rain. Pup. [40w are the w arious colours of the rai¡abow produced Tut. By the different refractions of the rays of the sun : the rays the least, refracted producing red; those the most refracted, violet; and the intermediate omes, the other colours. Pup. How comes the cold, or frost Tut. Frequently by the wind, which blows from the poles; and the stronger the wind, the severer the cold and frost. { \