PROGRESS OF METEOROLOGY IN 1889. 



227 



Barometer. 



Weak, easterly winds, north- 

 east to south. 



Neutral condition 



Stronj^ westerly winds, south- 

 west to north. 



Temp, below 0^ C . 

 Temp, flo to 15° C . 

 Temp, above 15° C. 



Above 



765""". 



.00 



00 



40 



{Meteor olofjische Zcitschrift, 1889, vi, .p. 348.) 



Balloon ohservatiom. — Lieutenant Modebeck has made a contribution 

 to the meteorology of tlie upper currents by observations made in a 

 balloon voyage March 31, 1888, from Berlin. The marked phenomenon 

 experienced was the influence of rivers. After the balloon had risen to 

 a height of 300 to 500 meters, it sank so rapidly while passing over the 

 Spree that when it was about 50 meters above the earth a large quan- 

 tity of ballast had to be thrown out. At an elevation of 1,200 meters 

 he met with a long narrow rain-cloud, in i)assing through which the 

 dry-bulb thermometer registered 1^.5 C, the wet bulb 1°C.; at an 

 elevation of 1,300 to 1,400 meters both thermometers registered the 

 same temperature, 2o.5 C. At this height, and in circumscribed areas, 

 a few very small semi-soft hailstones were observed. 



Soaring of birds. — Mr. G. K. Gilbert, in a paper read before the Phil- 

 osophical Society of Washington, shows that the soaring of birds is ren- 

 dered jwssible by the diflerential motions of the air. The following 

 paragraphs are extracted from his paper: 



"The soaring bird, with wings expanded, is formed so as to move 

 forward with little friction and downward with great friction. We 

 juay conceive him as having two coincident motions — a forward motion, 

 initiated by muscular action ; and a downward motion, under the pull 

 of gravity. In order that the resultant may be horizontal, it is neces- 

 sary (1) that the forward component be directed obliipiely upward, and 

 (2) that it exceed a certain minimum amount. 



" However small may be the friction created by the forward motion 

 it is not nil, and, unless the energy it consumes is in some way re- 

 placed, the forward motion is eventually so reduced that the horizon- 

 tal motion cannot be maintained. It is proposed to show that the 

 needed compensatory energy may be derived from the diflerential 

 motions of the air. 



" Let us assume that the air currents above and below a certain hor- 

 izontal plane have the same direc^tion but ditterent velocities, the ui)per 

 moving the faster by a certain amount, i. A soaring bird is moving 

 through the lower air in the opposite direction, and the bird's velocity 

 with reference to the air is V, then the velocity of the bird with refer- 

 ence to the upper current is T+t. 



