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 (u) 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^; -J^ = 2pa5 = the gradient G, and x = ^. 



From the equations^ - G sin a ^ 2wi; sin cp 



- G cos a = kv 

 Q 



2io sin w 

 we get tan a = j- — ^ 



„ 2(a QV sin (p 



fi sin a 



log fi = 6-08768 Q = [8-67545] g^Arj 



Taking the latitude ip = 82° and the friction coefficient k = 00007 we get 

 a = 64°. The mean pressure (6) 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 Osterreichischen Gesellschaft f(ir Meteorologie. Bd. XII, 1877, p. 52. 



