পাতা:পদার্থবিদ্যাসার.djvu/৫৫

44 Pup. Whatis hoar-frost? * , , , - fut. It is-congealed vapour. This also, as well as the show, falls in very beautiful forms, which are well worth minute inspection. Pup. What idea am I to form of thunder and lightning? Tut. Lightning is occasioned by the electric matter passing from one cloud to another. It explodes instantaneously like gunpowder, and is often accompanied with that awful roll, or sound, which we call 1hunder. Pup. What benefit is produced by lightning 2 Tut. It consumes noxious vapours, promotes a circulation of the air, produces rain, and tempers the 'summer heats. Pup. What produces thunder? Tut. The explosion of electric clouds, composed of sulphureous and nitrous, or other combustible substances, exhaled from the earth by the solar heat, and raised into the atmosphere. Thunder is also occasioned by the concussion of two bodies of air separated by the rapid motion of lightning. Pup. What occasions thunder tu make a rumbling moist. Tut. The echoes of the explosion. Pup. }iow is etio produced? Tut. From the undulations of the air upon walls, rocks, or other uneven bodies. * Pup. lf ihumder : is nothing more tham sound, I need not be afraid of what we call thunderbolts. Tut. Certainly not. All the danger arises from lightning; and even that is very harmless, when at a distance. - - -