REPORT OF THE SECRETARY. 37 



RESEARCH WORK. 



The exploration of the upper atmosphere by means of kites and 

 balloons has been continued at the Mount Weather Research Observ- 

 atorj', with satisfactory results. There were only nine days during 

 the year on which ascents were impracticable. The record of heights 

 reached shows that the majority of flights did not reach above 10,000 

 to 13,000 feet, only about 17 per cent of the total number exceeding 

 that elevation. On days when kites and captive balloons can not be 

 sent up, on account of unfavorable weather conditions, small balloons 

 are liberated, either singly or in tandem. Their first simultaneous 

 use in this country was made by members of the ^Mount Weather 

 Observatory in September and October, 1909, field parties having 

 gone to Fort Omaha, Nebr., and Indianapohs, Ind., for tliat purpose, 

 while a second expedition continued the experiments at Fort Omaha 

 in May, 1910. Of the instruments sent up in these small balloons, 

 12 out of 13 sent up from Fort Omaha and 6 out of 7 sent up from 

 Indianapohs were recovered after the first trip, while 15 out of 20 

 were secured after the second trip. 



The main difficulty met with in attempting to make satisfactory 

 scientific deductions from the fhghts is due to the varying heights 

 reached and to the differing weather concUtions under wliich they 

 are made, it being obvious that a direct comparison of atmospheric 

 conditions, one day with another, is not possible, unless daily records 

 are obtained from approximately the same levels. Xotwdthstand- 

 ing this the work of aerial research has already disclosed a number 

 of new and important facts, of which the following may be enumer- 

 ated: 



It lias been found, for example, that the stratification of the atmos- 

 phere as regards temperature and moisture is far more extensive 

 than was suspected. The accepted rule of decrease in temperature 

 with increase in altitude has many exceptions, a great layer of warm air 

 being frequently found floating upon a layer of cold air, wliile the tliick- 

 ness and horizontal extent of such warm masses have been found to 

 vary greatly. Again, temperature inversions have been recorded by 

 instruments at the time of ascent, whereas no trace remains when 

 the kite is brought down again a few hours later. Likewise the depth 

 of a given air mass changes with its onward movement past the line 

 of ascent and the \vind direction varies with different levels; some- 

 times when the surface wind is from the south, the direction half a 

 mile upward may at the same moment be from the southwest and 

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

 ments indicate that in this hemisphere the wind direction changes 

 to the right with increasing altitude, but kite and balloon observa- 

 tions show that it is also deflected to the left at times. It has also 



