OCR Text |
Show Atmosphere Above Earth's Surface. The atmosphere Is believed to extend ex-tend much more than 100 miles above the earth's surface. Its density decreases de-creases rapidly for the first few miles of ascent, then much more gradually. grad-ually. From the phenomena of twilight, twi-light, due to refraction of tight. It may be demonstrated that the air extends up to a height of 47 miles; but o'lo-r phenomena, such as the behavior of meteors and the aurora, show that rare air exists at a much greater height. |