MISCONCEPTIONS CONCERNING THE WEATHER 141 



has sometimes led people to conclude that the hailstones must have 

 necessarily come from the far north, falling as they do on days when the 

 heat has been oppressive. True hailstones occur only with storms of 

 the thunderstorm type, where violent convection extends to heights of 

 five miles or more above the ground. Here the ascending currents are 

 occasionally so strong that they carry aloft, far beyond the level of per- 

 manent freezing temperature, particles of moisture already condensed 

 into raindrops. In the average, there is a fall of temperature of 1° F. 

 for every 300 feet of height, so that even in midsummer, when the tem- 

 perature at the ground is 90° F., one has to ascend but 3| miles to 

 encounter a freezing temperature. The water droplets, solidifying upon 

 entering the freezing stratum of air, later fall to lower levels, where 

 they may again be caught up by ascending currents to the colder strata 

 above. This process may be repeated a number of times, with the result 

 that the hailstones, upon finally reaching the gi'ound, will show concen- 

 tric layers of ice and snow. The moisture content more probably came 

 from the Atlantic Ocean, to the east, or the Gulf of Mexico, to the south, 

 rather than from the far north. 



The development of meteorology and climatology has been so recent 

 that the general public has not kept pace vidth the progress. While 

 there are thousands of weather proverbs which are correct generaliza- 

 tions of weather observations extending over many years, a number of 

 traditions have persisted which are apparently without scientific foun- 

 dation. A few of these, originating in European countries, and doubt- 

 less true in their native environment, have proved inapplicable when im- 

 ported to America. Others are inadequate as they make no distinction 

 between the real and the apparent — between the objective and the sub- 

 jective. Still others are found wanting because they are based upon 

 fallacious ideas. Instrumental observations, laboratory experiments, 

 and the exploration of the free air have exposed many more misconcep- 

 tions. Though we have made but a small beginning in a systematic 

 science of the weather, we have advanced far enough to make it possible 

 to eliminate some of the earlier preconceived notions. 



