FOR HIGH I.EVELS IN THE EARTh's ATMOSPHERE. 75 



of the quantity E]j ;", and is constructed from the telegraphed values of El?" in a 

 manner analogous to the chart of II J""'"', page 67, Fig. 4. Tlie remaining maps on 

 page 71, viz., Figs. 13, 14, 15, present synoptic views of the distribution of the quan- 

 tities Er,!", EflJ:?, and El'?, respectively, and will be discussed later. 



The distribution of pressure under the prevailing dynamic conditions in the 

 atmosphere is thus presented on the one hand by j)^ charts, showing the isobars on the 

 level surfaces of gravity, and on the other hand by Vp charts, showing tlie level lines 

 of gravity on the isobaric surfaces. These two systems of charts taken together 

 present a very clear picture of the relative positions of the isobaric surfaces and of the 

 level surfaces of gravit}'. From kite observations and by the aid of the tables accom- 

 panying this memoir, isobars on the level surfaces of gravity can be constructed for 

 much smaller intervals, i. e., for the level surfaces of F= 0, T^= 10 000, F = 20 000, 

 ... F = 180 000, as also level lines on the isobaric surfaces of j) = 31, p = 30.5, 

 J) — ZO.O ■ ■ -p = 19.0. The charts on pages 67, 69, 71, however, suggest that such 

 intervals are much too small. In fact, the charts for jVgoooo- i'4oooo> and jh show nearly 

 the same characteristics ; and the same is true of the charts for F25.0 and 1^27.5- It is 

 obviously superfluous to draw charts for such small intervals that the types are nearly 

 identical. On the other hand the interval must not be too large since then the 

 features would differ so much that it would be difficult or impossible to follow the 

 continuity of the change in the type with increasing elevation. We must learn 

 through experience what intervals are to be chosen as best suited to our studies, and 

 to the condition of the atmosphere. 



I have chosen the isobaric map drawn for sealevel as the base for the py- and 

 T'^-maps, because the values of atmospheric pressures as telegraphed from permanent 

 observing stations are, without exception, reduced to sealevel. But when one wishes 

 to construct maps for the free atmosphere, it is quite superfluous to first reduce the 

 pressure to sealevel, and then re-reduce it upwards from sealevel to a higher one. The 

 rational way would be to reduce the pressures observed at the permanent stations, not 

 to sealevel but to the nearest level surface of gravity for which a j:)^map is to be con- 

 structed, and then use the value of p,r thus obtained in constructing the corresponding 

 p,^map. In an analogous way the number of level surfaces of gravity lying between 

 the level of the station-barometer and the nearest isobaric surface adopted for map- 

 ping values of Vp, might be calculated ; whence by adding the values of Fq, the values 

 of Vp for the isobaric surface in question could be determined and be used in con- 

 structing the proper P^-map. The values of Pf. and F^ obtained from the kite-obser- 

 vations would thus serve in constructing their respective maps for the free air and the 

 values of n['; and. E^^ could be used in the manner already described, for superposition 



