Aerial Navigation. 389 



Academy, desirous of rendering these experiments useful, 

 had made a trial of the different processes for ascertaining 

 the direction of an aerostatic machine, when its elevation 

 does not -admit of its being seen from the earth, and when 

 there remains no object with which it can be compared. 

 The process which these philosophers employed is both in- 

 genious and simple. It Consists in attaching to the car, by 

 a silk thread, a float, or .very light log, which by its posi- 

 tion always indicates the direction, the ascent or descent of 

 the balloon, even before the barometer has made the least 

 movement. By means of a powerful achromatic telescope, 

 which traversed in a perpendicular direction the bottom of 

 the car, the observers were enabled to distinguish the spot 

 over which the balloon hovered ; and in this manner they 

 ascertained the moment when they entered the Gulph of 

 Bothnia, and the time when they got out of it. They 

 made experiments also on the echo of sound, the reflection 

 of which is exceedingly sensible and calculable in the upper 

 strata of the atmosphere. It is believed that during their 

 next ascent they will endeavour to determine the difference 

 of the ratios between the ascent of sound and its propaga- 

 tion in a horizontal direction. The observation made by 

 Mr. Robertson, when he ascended at Hamburgh on the 

 18th of July 1803, is confirmed by M. Sacharof. The 

 north pole of the dipping-needle was raised ten degrees, &c. 

 The existence of a superior current, which twice drove the 

 balloon towards the sea, prevented the travellers from 

 rising so high as they intended. The mercury in the baro^ 

 meter fell eight inches and a half. Tiie thermometer, which 

 indicated thirty degrees at their departure, stood at three 

 degrees at the highest elevation. They remained four hours 

 in the air, and descended at the distance of twenty-five 

 leagues from the place of departure. 



Venice, Aug. 25. 



Count Zambeccari, whose unfortunate aerial journey, 

 from Bologna across the Adriatic sea to Pola in Istria, is 

 still fresh in the memory of the public, undertook a new 

 voyage last week, and from the same place. He was sa- 

 luted at first with loud acclamations from the manv thou- 

 sand spectators, because he made the balloon rise and fall 

 at pleasure. At the end of four hours, when hovering over 

 the village of Cao, some flasks filled with spirit of wine 

 caught fire. He immediately descended ; and M. Andreoli 

 his companion, jumped from the balloon, in order to secure 

 it by fastening the anchor. Count Zambeccari was desirous 

 -of getting out also; but before he could accomplish it, the 



Vol. 10, No. 76*. Sept. 1S04. D d b alloou 



