190 ANNUAL REPORTS OF DEPARTMENT OF AGRICULTURE. 



but a short distance into the air, thus making it impossible to follow 

 the changes from one day to the next wlicn the flights were of unequal 

 altitude. In the five years' campaign, however, the observatory has 

 succeeded in locating the dangerous sectors of a storm and in roughly 

 determining from surface conditions when it is unsafe to navigate 

 the air. The service thus rendered to the science of aviation will be 

 more fully appreciated as time passes. 



It may properly be said that the kite force at the Mount Weather 

 Observatory brought the art of kite flying for meteorological pur- 

 poses to the highest state of proficiency ever attained in this or any 

 other country. On May 5, 1910, 10 kites, with 11.5 miles of wire, 

 carried a recording instrument to an altitude of 4.5 miles above sea 

 level, the greatest altitude ever reached by a kite. From July 1, 

 1907, to June 30, 1912, 1,772 kite flights or captive-balloon ascensions 

 were made, mostly in the level below 3 miles. 



USE OF BALLOONS. 



Meanwhile the observatory had extended its work to the explora- 

 tion of the region bej^ond the level attainable by kites. This higher 

 stratum was reached by means of small rubber balloons filled with 

 hydrogen gas. The ascensions were made at points in the West, 

 where of the 91 balloons sent up 79 were recovered with good rec- 

 ords. These records afford the only direct measures hitherto obtained 

 of the temperature and moisture of the air at very great altitudes, 

 and also furnish information respecting the direction and speed of 

 the wind for the same region. On September *1, 1910, a balloon 

 launched at Huron (S. Dak.) reached the extraordinary height of 19 

 miles above sea level, the highest point to which a meteorological 

 instrument has ever been carried and aftenv^ards returned safely to 

 the earth. 



These observations at great altitudes suggest that possibly the 

 changes in the weather experienced at the surface of the earth orig- 

 inate in the levels between 9 and 15 miles above and that they are 

 propagated downward. The basis of weather forecasting rests upon 

 the fact that, for the most part, changes in the weather advance from 

 west to east. If, instead of advancing horizontally over stretches of 

 hundreds of miles, the seat of weather activity should rest less than 

 15 miles above us, the failure to improve forecasts based on a hori- 

 zontal translation of weather conditions can readily be understood. 



Experimental work is still being carried on at Mount Weather on 

 practical problems as they arise. Aerial soundings are being made 

 on special days, with a view of determining the height in the free 

 air to which a diurnal wave in the temperature, moisture, and wind 

 conditions can be traced. It is expected that this problem will be 

 solved within the ensuing year. 



