502 ANNUAL EECORD OF SCIENCE AND INDUSTRY. 



above the horizon, the atmosphere, which was very dry, sucU 

 denly became charged with electricity, whose quantity di- 

 minished gradually with the increasing intensity of the sun's 

 rays. During the latter portion of the journey, being in the 

 neighborhood of the sea, the passage of the balloon from 

 an upper to a lower current of air was made eight times 

 successively. The lower current had apparently a depth of 

 only 150 meters; the upper current, on the contrary, pre- 

 vailed uniformly above this elevation, being always from the 

 southwest to the north-northeast, and opposed to the lower 

 current. In the early morning hours the temperature of the 

 air was always found to be, at all altitudes, decidedly higher 

 than at the surface of the ground. 13 J5, III., 293. 



AERIAL NAVIGATION. 



Aerial navigation has in no country been more diligently 

 studied and more perseveringly essayed than in France; 

 and of those who have distinguished themselves in this line 

 of invention Penaud is among the first. In a recent com- 

 munication to La Nature, he gives a short sketch of the 

 best of the various kinds of apparatus for mechanical flying. 

 He states that the war of 1870, by its stimulating balloon- 

 ing*, has also turned the thoughts toward the brilliant future 

 that possibly exists for artificial flying; and he hopes that 

 France, which has given the balloon to the world, will also, 

 in the end, put to shame the ridicule of those who disbelieve 

 in artificial flying machines. These, as at present known, 

 are classed under the three heads of helicopters, or the helix 

 bird, aeroplanes, and orthopteres. The helicopters are sus- 

 tained in the air by the aid of helices, whose axes vary a lit- 

 tle from the vertical ; their movement of translation may be 

 brought about either by helices suspended from the oth- 

 ers, or by the aid of special propelling helices. The orthop- 

 teres are surfaces, very nearly planes, inclined at a small 

 angle to the horizon, and pushed horizontally by propellers 

 which are in general helices. Finally, orthopteres have, as 

 their principal organs, surfaces which have movements very 

 nearly vertical, and frequently alternating; and under this 

 latter system are classed the wings of birds, surfaces having 

 movements like the tails of fishes. Among the many de- 

 scriptions which he gives of the special inventions included 



