Explorers of the Air.

Kaipara and Waitemata Echo, 3 April 1914, Page 8

Explorers of the Air.

The limit to which manned balloons can ascend is about 30,000 I'eoL, but a sounding balloon lately sent up in Italy at the University ol Pavia, reached a height of 121,000 feet, or nearly 23 miles. The sounding balloons, the modern device for exploring the upper air, are usually hags of silk or rubber, about six feet in diameter, filled with hydrogen gas. They rise until the pressure of the gas causes them to collapse or explode, and a parachute then brings dow<n safely the story of the air passed through, as taken down automatically by a special apparatus. This apparatus, called a meteorograph," combines several instruments in one. It has an accurate chronograph for time, an. aneroid barometer for height or atmospheric pressure, a metallic thermometer for temperature, a hair hygrometer far relative humidity, and an anemometer for wind velocity, and each instrument gives a continuous record by means of a pen resting on a rotating cylinder covered with ruled paper. The most remarkable fact shown by these balloon soundings of the last 10 or 12 years is that the air exists in two very distinct layers. In the lower layer, or "troposphere," the air cools about 1 deg. Fahrenheit for each 300 feet of ascent ; but m the upper or isothermal layer, or "stratosphere," further ascent gives stationary or rising ' temperature. The upper limit of the isothermal layer is unknown. The lower limit—lower in winter than in summer—has an average height of about six miles in middle latitudes, but is lower near the poles, and reaches a great height at the equator. The temperature of this layer ranges from to 71 deg. below in winter.