174 DYNAMIC METEOROLOGY AND HYDROGRAPHY. 



great reserve. The same should be the case along the borders of the chart. But in 

 the more central part, in the Mississippi valley, we have every reason to believe 

 that the chart gives a good approximation to the truth. The question of attaining 

 the same reliability of the chart of acceleration in the other districts will, as will be 

 understood at once, simply be a question of further developing the net of stations 

 and improving the methods of observing the wind. 



204. Main Example of Kinematic Diagnosis, Europe, 1907, July 25, 7 a. m. 

 Greenwich. In the preceding examples we have exclusively used observations from 

 the common meteorological stations at the ground. We shall now consider a case 

 where observations, though in quite insufficient number, are at hand also from the 

 higher strata, namely, the aerological observations on the morning of July 25, 1907. 



To begin with the observations from the ground, plate LI I gives the distribution 

 of pressure and of mass in the lowest atmospheric sheet. The single lines give the 

 absolute topography of the 1000 m-bar surface and the double lines the relative 

 topography of the 900 m-bar surface. It will be seen that pressure is rather uni- 

 formly distributed. A relatively high ridge goes from Iceland over Scotland and 

 the North Sea toward the Balkan Peninsula. East of this ridge a great number of 

 local maxima and minima are seen. Plate LIU gives the winds observed, represented 

 by arrows, by numbers of direction, and by numbers of intensity. The winds are 

 generally faint and irregularly distributed. 



Plate LIV gives the corresponding continuous representation by use of isogonal 

 curves and curves of equal intensity. The diagram of isogons shows a great number 

 of positive and negative singular points. Plate LV gives the representation by lines 

 of flow and intensity-curves, with the corresponding great number of neutral points 

 as well as of points and lines of convergence and of divergence. The comparison 

 with the chart of pressure plate LII shows that the points of convergence with great 

 regularity coincide with the small depressions, and the points of divergence coincide 

 with the corresponding heightening of the isobaric surface of 1000 m-bar pressure. 



The chart of plate LIV is drawn upon a blank which represents the average 

 pressure at the ground (see plate XXX) . From this chart we therefore easily derive 

 that of vertical specific momentum at the ground, plate LVI. 



When we pass to air-motion in the higher strata, we must limit our considera- 

 tions to the small area where we have the closest network of aerological stations. 

 We have done this on plates LVI I to LX, which correspond respectively to the 

 standard sheets X, IX, VIII, and VII (section 107). The incomplete sheet XI is so 

 thin that we have left it out of consideration. The wind-observations are represented 

 on the charts A of these plates by arrows and intensity-numbers, as we have men- 

 tioned already. As the arrows and numbers are too few in number for the drawing 

 of the charts of horizontal motion, we have used in anticipation dynamic principles 

 for giving at least a tolerably probable reconstruction of the horizontal motions as 

 developed in section 139. The reconstructed horizontal motions are represented by 

 lines of flow and curves of equal intensity on the charts B of plates LVI I to LX. Of 

 course we must leave open the question regarding the degree to which we have thus 



