ON THE FIRST OBSERVATIONS WITH REGISTRATION 

 BALLOONS IN AMERICA. 



By A. Lawrence Rotch. 



Presented March 8, 1905. Received July 22, 1905. 



In a communication to the Academy in 1897,* the author described 

 the so-called " ballons-sondes," which had been first employed in Europe 

 a few years before to ascertain the meteorological conditions of the high 

 atmosphere. He also gave an account of the more recent use of kites at 

 his own Observatory on Blue Hill to investigate the conditions prevail- 

 ing in the free air at lesser heights. In concluding he expressed the 

 wish, as the American member of the International Committee for Scien- 

 tific Aeronautics, that similar explorations of the high atmosphere with 

 the " ballons-sondes " might be attempted in America. 



Although the successful experiments at Blue Hill led to the extensive use 

 of kites for meteorological observations abroad, the " ballons-sondes" were 

 not tried in America until 1904, when the author was enabled to make 

 a series of ascensions at St. Louis through the co-operation of the man- 

 agement of the Lousiana Purchase Exposition. A grant of $2,500 was 

 authorized, but only about half this sum was spent for apparatus, travel- 

 ling and living expenses. 



In Europe two types of these balloons have been employed recently ; 

 viz., large balloons of silk or paper and small balloons of india-rubber, all 

 being filled with hydrogen gas. The economy and ease of inflation, 

 with the advantage of a quick ascension to the culminating point and re- 

 stricted drift, led to the adoption in the St. Louis experiments of the 

 latter form, devised by Dr. Assmann, director of the Royal Prussian 

 Aeronautical Observatory, and made by the Continental Caoutchouc and 

 Gutta Percha Company of Hanover, Germany. The balloons used had 

 an initial diameter of approximately six feet when inflated with about 

 100 feet cubic feet of hydrogen gas, and carrying parachute and in- 

 strument exerted a net lift of nearly two pounds, which is sufficient. 

 Being closed at the mouth they rise at an almost uniform rate of speed, 

 expanding meanwhile until they burst at a height which is dependent 



* These Proceedings, 32, No. 13. 



