FOR HIGH LEVELS IN THE EARTHS ATMOSPHERE. 81 



earth's rotation, then this solenoid-system would have produced a mean velocity of 0.8 



, along the curve by the end of the first hour. At the end of the second hour 



hour ° -^ 



the mean velocity would be 1.6 , — ; at the end of the third hour 2.4 ^ and so 



hour hour 



on. By carrying out a number of such numerical calculations on the E]J;-map one 



will soon become so familiar with tlie dynamic significance of its lines that a glance at 



the chart will suffice to recognize and read the accelerations indicated by it. 



The EP g-map may be constructed directly from the values telegraphed to the cen- 

 tral office ; but after the complete results of the kite-observations at the different sta- 

 tions have been received by mail these maps may be constructed for much thinner 

 strata in the atmosphere. Then, for instance, the layer of air between the isobaric 

 surfaces for p = 27.5 and }) = 25.0 can 'be subdivided into five strata whose dynamic 

 condition can be presented by charts for E;;.?, ^-l, Ei^;?, E^.o, Et?. On page 71 only 

 three of these latter maps have been drawn, viz., for E'^j-j as Fig. 13; Ejljj as Fig. 14 ; 

 and Eals as Fig. 15. From Fig. 13 it is seen that in the layer of air between the iso- 

 baric surfaces of 27.5 and 27.0, the maximum ascensive tendency is southeast of 

 Topeka. The E^^g-map, Fig. 14, shows that in the layer between the 26.5 and the 26.0 

 isobaric surfaces the air has its maximum ascensive tendency just over Topeka. The 

 E^Jig-map of Fig. 15 shows the maximum ascensive tendency to be above Pierre and 

 Dodge City. If we neglect this shift of the center of ascension toward the northwest 

 then we find that the solenoids as drawn for the thinner strata have nearly the same 

 characters as those drawn for the larger interval of the E^j-map. It suffices, there- 

 fore, to construct E^;-maps for thicker strata or greater intervals by aid of the tele- 

 graphic reports and afterward for smaller intervals by means of the more complete 

 reports by mail. In this way very brief condensed telegraphic reports may be made 

 to do good service. 



The general expression for the number of solenoids within a closed curve consist- 

 ing of two verticals a and /;, and two curves lying in the isobaric surfaces ^j = p^ and 

 p =pu is 



^ = iKX-iK\ (28) 



This may be deduced in exactly the same way as the special formula equation (27). 

 It follows from equation (28) that each of the tubular-shaped figures in the atmosphere 

 bounded by the isobaric surfaces ^J = Pi and p — p^, and the vertical walls, passing 

 through the curves drawn on such a map, contains a number of solenoids equal to the 

 number obtained by subtracting the numV)er3 belonging to those latter curves. 

 Hence it follows that in the maps forming Figs. 13, 14 and 15 of page 71 designated 



