পাতা:পদার্থবিদ্যাসার.djvu/৪৩

3? -$7%t. Eight hundred and sixteen times. : Pup. Whai weight - of. air is supposed to rest on the body of a middling size person 2 - - -Tut. About one ton and a half. -- 'Pup. How does it happen that this weight is not perceptible? - Tut. Because, the spring of the air, which is within the human body, re-acts with an equal sorce against the outward pressure of the air. Pup. What is ille whole weight of the atmosphere computed to be? . - Tut. 11,522,211,494,2os,773,089 lbs. : Pup. What is the wiud?, t } Tut. The wind is nothing more than a part of the air put into motion. t Pup., From what cause does this rise? Tut. Principally from the warmth or cold which is excited in the air. Heat expands the air, and cold condenses it. Still it is difficult to account for the changes that take place with regard to the wind. It is generally supposed that the air less rarefied by the heat, rushes into that more rarefied, and produces wind, • , . Pup. Have you any particular mames, by which to distinguish the winds? - -- Tut. They are called, according to the quarters from which they blow, East, West, North, and South. Pup. , Will you please to tell me how to find these quarters? " t Tut If in the ständ with your face to the "sun, the east is before you, the west behind you, the south to your right, and the north to your left: or at night, if you stand with yourface to the pole star,