120 



DYNAMIC METEOROLOGY AND HYDROGRAPHY. 



concentration of mass in the center of the cyclone. We indicate this only to point 

 out what the charts tell, not to discuss the fact in itself. For we have refrained 

 from discussing the reliability of the observations from which charts have been 

 deduced, our only aim being at present to illustrate our methods, the observations 

 being given and considered as trustworthy. 



Table T. Pressure (tn-bars) in standard level surfaces and differences of pressure 

 between them, computed from ascents, Europe, November 7, IQOI. 



72. Unit-Tubes. The two sets of curves in figs. 17, 18, 21, and 24 divide the 

 vertical plane into a set of curvilinear parallelograms. These parallelograms are 

 evidently the cross-sections of a set of tubes formed by the intersection of the two 

 sets of surfaces. We may denote them as isobaric-isosteric tubes when they are 

 formedby intersection of the isobaric and the isosteric surfaces (figs. 17 and 21), and 

 as equipotential-isopycnic tubes when formed by intersection of the equipotential 

 and the isopycnic surfaces (figs. 18 and 24). They may further be called unit-tubes 

 if the intersecting surtaces are drawn for unit-differences of the scalar quantities 

 whose fields they represent. The name unit-tubes may be retained also in case of 

 the one set of surfaces being drawn tor intervals of a certain multiple of the unit, 

 while the other set is drawn for intervals equal to the corresponding fraction of the 

 unit. In figs. 17 and 21 are isobaric curves drawn for every centibar and isosteric 

 for every 10 m 3 /tons. Every parallelogram therefore represents 10 m. t. s. unit 

 isobaric-isosteric tubes. In figs. 18 and 24 a level line is drawn for every 100 

 dynamic meters, i. e., for every 1000 dynamic decimeters, while the isopycnic curves 

 are drawn for every hundred-thousandth ton/m 3 . Every parallelogram in these 

 figures thus represents one-hundredth of a m. t. s. equipotential-isopycnic unit-tube. 



In case of true equilibrium there will be no intersection of the surfaces and 

 therefore no tubes. On the other hand, as the angle of intersection increases, the 

 number of unit-tubes will increase. This number can therefore be taken as a 



