250 PROCEEDINGS OF THE AMERICAN ACADEMY. 



and a free balloon, both equipped with self-recording instruments. The 

 latter, called the Cirrus, of 8,830 cubic feet capacity, when inflated with 

 coal-gas had a lifting force of about 290 pounds, besides its envelope 

 weighing 93 pounds, and the meteorological apparatus weighing nearly 

 6 pounds. This is more complicated than the French instruments, since 

 the registration is photographic, and a continuous ventilation of the alco- 

 hol thermometer in Assmann's aspiration aj^paratus is effected by allow- 

 ing a weight to drive the aspirator. Even with these precautions, the 

 temperatures are probably too high, and the registration is often defective. 

 There have been seven fli";Iits of the Cirrus, one of the hisrhest occurring 

 in September, 1894, when the uuprecedentedly low barometric pressure 

 of about two inches of mercury was recorded, giving a computed height 

 of 60,500 feet. The lowest tempei-ature, which was registered at a 

 somewhat less altitude, was not below — 88° Fahrenheit, giving rise to 

 the supposition that the thermometer was heated by insolation. Hence 

 the average decrease of temperature appears to have been but 1° in 

 409 feet. This balloon rose from Berlin with the great velocity of about 

 30 feet [ter second, and travelled 5G0 miles in an east-northeast direction 

 at a velocity of 83 miles per hour. 



For some time past negotiations have been in progress between the 

 French and the Germans for simultaneous ascents of unmanned balloons 

 at night, using identical instruments, whereby the errors due to insolation, 

 and the discrepancies which might be attributed to different instruments, 

 would be avoided. By this co-operation the simultaneous conditions of 

 the upper air over a wide extent of country can be ascertained, just as 

 these conditions near the earth's surface are daily obtained at the meteoro- 

 logical stations in the different countries. The desired result was brought 

 about by the International Meteorological Conference which met last 

 September in Paris. Resolutions were adopted favoring scientific ascents 

 with manned balloons, as well as simultaneous flights of unmanned regis- 

 tration balloons in the different countries. The successful use of kites at 

 Blue Hill to lift self-recording instruments over a mile into the air, led to 

 expressed desire that similar experiments should be tried elsewhere. An 

 international committee was appointed to carry out these resolutions, 

 consisting of Messrs. de Fonvielle and Hermite for France; Assmann, 

 Erk, and Hergesell for Germany ; Pomortzeff for Russia ; and the writer 

 for the United States. In accordance with the first named resolutions, a 

 flight of four manned and four registration balloons occurred in France, 

 Germany, and Russia on the night of November 13-14 last. Owing to 

 hurried preparations, only the registration balloon liberated from Paris 



