ATMOSPHERE IN RELATION TO HUMAN LIFE AND HEALTH. 317 



over the equatorial region, aud that a slower movement of the upper 

 air from southwest and west prevailed iu autumn over the northern 

 temperate zone. Investigation of the currents of the atmosphere at 

 heights exceeding 40,000 feet is likely to lead to valuable results. 

 Exploring balloons might even show the ultimate possibility of rapid 

 communications between distant places by means of steady upper 

 currents. 



Part IV. — Subjects for Kesearch. 



The following subjects for research seem likely to yield valuable 

 results in connection with the welfare of man. The bearing of some 

 of the points suggested may be slight or remote, but are not on that 

 account altogether negligible: 



The topographical features of different countries in relation to cli- 

 mate and weather, and a comparison of the effect on weather and 

 climate of similar physiographical features and circumstances in dif- 

 ferent zones and climatic areas. 



The influences of forests and cultivation on weather, on humidity, on 

 atmospheric electricity, rainfall, thunderstorms, soil moisture, and the 

 flow of rivers. 



The influence of the radiation from different soils and surfaces on 

 climate, as, for instance, of grass compared with fallow, aud of sand 

 compared with rock and clay. 



The heat received by the soil from the sun in different climates and 

 at different altitudes. 



The intensity of solar radiation at different latitudes and altitudes. 



The intensity of terrestrial radiation into space by day and night at 

 different altitudes, and the temperature of small objects suspended 

 at high altitudes in sunshine and at night. This might be obtained 

 by exploring balloons. 



The temperatures of clouds of different thickness and different char- 

 acter in their upper, lower, and central parts, and at a little distance 

 outside them. 



The causes of the down rush and increase of horizontal movement of 

 the air often observed before heavy showers and hailstorms. 



The dynamical and thermal consequences of the rising and falling of 

 masses of air. 



The action of air in motion, or wind, on calm or stagnant air near 

 their bounding surfaces; the manner in which by friction and by impact 

 masses of air influence other masses whether at rest or in motion, and 

 the effects of the collision of meeting masses of different specific gravity 

 and humidity. 



The influence of clouds of various thicknesses and heights on the 

 radiation from the earth's surface. 



The nature of the vapor or invisible water screen which often arrests 

 radiation on clear nights. 



