212 EFFECT ON LIFE OF BAROMETRIC PRESSURE 



the lower strata are laden, and the propinquity of the higher 

 strata to space. The radiant heat of the sun, on the other hand, 

 is much greater at high altitudes owing to the diathermancy of 

 air, and the absence of dust and water particles which scatter the 

 rays in the lower strata. The velocity of the wind increases in 

 the higher regions of the atmosphere as the friction against earth 

 and the denser lower strata decreases, while the slope increases 

 down which the air raised by the tropical heat flows towards the 

 poles. These factors, together with the dryness of the atmosphere 

 and the lessened C0 2 and 0. 2 tension, have great influence on the 

 existence of life in high altitudes. The freedom of the air from 

 bacteria is complete there are only 150 dust particles per c.c. 

 of air on Mont Blanc against 150,000 in cities under the worst 

 conditions. "I had forgotten a wallet on the Matterhorn," said 

 a guide, "in which there was some bread and cheese, and last year 

 I found it again and ate up the contents, which were not at all 

 musty." Ropes and ladders last for years which would have 

 rotted in the valleys. 



Water boils on Mont Blanc at 84' 3 C. owing to the 

 diminished barometric pressure. In Pike's Peak Observatory 

 (14,147 ft.) a pan full of loose snow was set on the hot stove 

 to melt, and in a very short time the water in the bottom 

 of the pan began to boil, while the snow on the top of it 

 was yet 3 to 4 inches deep. Fuel burns with difficulty owing 

 to the diminished pressure of oxygen. Thus the oil burnt in 

 an asbestos wick lamp in a given time was 2-193 grm. at 

 760 mm. Hg and 1-9119 grm. at 360 mm. Hg. The electrical 

 potential in the region of lofty peaks is often very high and 

 produces striking effects. 



The air is ordinarily charged with a certain amount of posi- 

 tive electricity while the earth is usually negative. Increase in 

 electrical potential is caused by the masses of water vapour 

 which, rising from the sea or snow-fields, become condensed. As 

 the tiny droplets unite in the clouds to form larger drops, the 

 electrical charges which always exist on their surfaces become 

 added together. Since the surface of the drop is far smaller than 

 the surfaces of the combined droplets, the electrical potential 

 increases with the condensation. Such condensation takes place, 

 particularly when warm air from the plains is forced up mountain 

 slopes. Darwin, speaking of an experience in the Andes, says, 



