586 H. MOHN. METEOROLOGY. [norw. pol. eXp. 



The rate of the propagation of the barometrical minima cannot be properly 

 found from observations from a single place. In order to arrive at an opinion 

 as to this rate in the Arctic Ocean, I have made the following computations, 

 requesting that they may be looked upon as mere experiment. 



The curve representing the values of the pressure in a regular barome- 

 trical depression takes a sinusoid form in the vertical section through the 

 axis. This may be represented by parts of similar parabolas, one with a 

 vertical axis upwards through the centre, and two congruent pieces of parab- 

 olas with vertical axis downwards, one at the front and one at the end of 

 the depression. The parabolas meet on each side of the centre in symme- 

 trical points situated at half the height of the total depression and at a 

 distance from the centre of half the radius of the depression. In these points 

 occurs the maximum dip of the curve or of the gradient, and also the maxi- 

 mum of the velocity (v) of the wind. The abscissae (x), reckoned horizontally, 

 are measured in degrees of meridian, and the ordinates [y] in millimetres. 



We have then in the parabola 



y = px^; -^ = 2px = the gradient G, and x= -M-. 



From the equations ^ — (? sin a = 2wd sin cp 



- Q cos a = kv 

 Q 



2w sin rn 

 we get tan a = ^ — - 



„ 2w pv sin q) 



fi sin a 



log 1^ = 6-08768 Q = [867545] g^gV^ 



Taking the latitude ^ = 82° and the friction coefficient k = 000007 we get 

 a = 64°. The mean pressure (&) being 750 mm., and the mean minimum 

 pressure about 740 mm., I take for the maximum wind-velocity y = 10 mm. 

 The mean temperature of the 73 depressions is — 24-°5. The velocity of the 

 wind, the mean maximum, taken from the table on p. 306, equals 97 m. p. s. 



» Zeitschrift der esterreichischen Gesellschaft fiir Meteorologie. Bd. XII, 1877, p. 52. 



