THE OBSERVATIONS OF AIR AND SEA MOTIONS. 1 9 



six days, extending from July 22 to July 27, during which the North Pole was sur- 

 rounded by a circle of aerological stations. During this period in all 89 registering 

 balloons, 20 manned balloons, 100 kites and captive balloons, and 41 pilot-balloons 

 were sent up. 



From our point of view these observations were spread out over too great an 

 area as well as over too long a period of time. The number of pilot-balloons launched 

 was also far too small compared with that of registering balloons (compare sections 

 92, 93). In order to try a diagnosis of atmospheric motions we can only think of 

 using the observations from a more limited area, where the network of stations was 

 closest, namely, central Europe. And we shall choose the epoch when the greatest 

 number of fairly simultaneous ascents took place, namely, July 25, about the time 

 of the daily meteorological observations, 7 a. m. Greenwich. From one hour 

 before to two hours after this epoch 13 balloons were followed by theodolites. This 

 number is not sufficient for working out a real diagnosis of atmospheric motions 

 over Central Europe, but we shall at least be able to illustrate the formal methods. 



When working out the example we shall choose the method of dividing the 

 atmosphere into isobaric sheets ; the corresponding use of level sheets will be under- 

 stood without difficulty. Using the methods developed in vStatics, as well as those 

 given in section 105, we get the result of the ascents condensed in table D. In 

 each of the 13 subdivisions of this table, the first column gives the standard pressures 

 and the pressure at the station ; the next gives the dynamic height of these pressures, 

 and the three following the thickness of sheets, direction, and velocity of air-motion 

 in the sheets. It may be remarked regarding the observations that those of the 

 wind in subdivision 8 are obtained from the ascent of a kite, those in subdivisions 1 1 

 and 12 from the course of manned balloons. The registering balloon, subdivision 13, 

 could not be viseed for cloudiness. In subdivision 7, heights of standard surfaces 

 and thickness of standard sheets are estimated from the ascents at the other stations. 



From the numbers registered in table D we shall now work out the corre- 

 sponding synoptical representations. Using the numbers representing the heights 

 of the standard isobaric surfaces and the thickness of the sheets contained between 

 them, we shall first work out representations of these sheets. For the sake of brevity 

 we shall denote these sheets, counted from below, by the Roman numbers X, IX, 

 VIII, . . . , X being the sheet limited below by the 1000 m-bar surface, IX that 

 limited below by the 900 m-bar surface, and so on. The always incomplete sheet 

 contained between the 1000 m-bar surface and the ground may be denoted by XL 



To distinguish the curves for absolute and those for relative topography we 

 shall draw the first as single and the second as double lines. The double lines con- 

 sist of a thick and a thin line, the thin being drawn on that side where the isobaric 

 sheet, whose thickness is represented, is thinner. Fig. A of plate LVII represents 

 the isobaric sheet X, the single lines giving the dynamic height of the 1000 m-bar 

 surface above sea-level and the double lines giving the height of the 900 m-bar 

 surface above the 1000 m-bar surface. Or, as we express it: 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. In the same manner fig. a of plate LVIII 



