WEATHER BUEEAXJ. 163 



dianapolis used hydrogen gas generated on the ground by the iron 

 filings-sulphuric acid process, using a portable generator. As the 

 gas thus generated did not have the lifting power of that used at 

 Fort Omaha, two balloons instead of one were used at Indianapolis, 

 which necessarily reduced the number of synchronous ascensions. 

 Twelve of the 13 instruments sent up from Fort Omaha and 6 of the 

 7 sent up from Indianapolis were recovered. 



The mean of the highest altitudes reached at Fort Omaha was 13.3 

 kilometers, or about 8.3 miles. The greatest altitude reached was a 

 little over 24 kilometers (15 miles). The average height of the In- 

 dianapolis ascensions was 14.6 kilometers, about 9 miles, and the 

 height of the highest individual ascension at that place was 19.4 

 kilometers, or about 12.5 miles. 



The detailed data of pressure, temperature, moisture, and direc- 

 tions of the wind for all of the flights will be published in a report 

 already prepared by Research Director W. R. Blair. 



A sounding-balloon expedition to Fort Omaha was made by a party 

 from the ]\Iount Weather Research Observatorv in May, 1910. Fif- 

 teen out of 20 instruments sent up on this expedition were recovered. 

 The altitudes attained were not great, owing, apparently, to a poor 

 quality of rubber in the balloons, which permitted the gas to escape. 



Notwithstanding the difficulties encountered in aerial research, 

 the work thus far carried on at Mount Weather has disclosed the 

 following new and important facts : ' 



The stratification of the lower portion of the atmosphere, as re- 

 gards its temperature and moisture, is more extensive than was 

 hitherto suspected. It has been known for many years that the tem- 

 perature of the air diminished with increasing altitude, but the de- 

 tails remained more or less obscure until revealed by the daily records 

 brought down by kites and balloons. It has been found that there are 

 many exceptions to the rule of decrease of temperature with increase 

 of altitude; thus, a great layer of warm air is sometimes found 

 floating upon a layer of cold air ; and furthermore the thickness and 

 horizontal extent of such masses of warm air may vary greatly. 

 Columns of warm air over a mile in vertical extent have been meas- 

 ured. Again, kite ascensions have disclosed temperature inversions 

 of which no trace remained on the descent of the kite a few hours 

 later. These evanescent inversions are probably produced by small 

 masses of relatively warm air flowing across the line of ascent. 



The kite flights have also thrown new light upon the direction and 

 the depth of air currents from the surface to the highest altitudes 

 attained. The various strata of air flowing past a place of observa- 

 tion are not of uniform depth and direction from the surface up, as 

 might be supposed, but are at times composed of layers, each differing 

 somewhat in direction from the next adjoining layer. The direction 

 of the surface wind may be from the south, and at the same moment 

 the direction a half mile upward may be from the southwest, and 

 a half mile above that level it may be from the west. 



It was known from observations of the clouds that in this hemis- 

 phere the wind was deflected to the right with increasing altitude 

 above the ground, but the kite and balloon observations show that at 

 times it is deflected to the left. It has also been found that the depth 

 of easterly winds on this continent is less than over northern Europe, 



