148 



DYNAMIC METEOROLOGY AND HYDROGRAPHY. 



When we use the decibar as unit pressure the upper limiting surface of the 

 sheet will be situated at the approximate height of 750 meters above the ground. 

 The lines of flow represent vertical walls which divide this sheet into tubes. At the 

 initial wall C the transport in each tube is 5.10 5 m.t.s. units, i. e., 500,000 tons of 

 air per second. As we proceed from the curve C to other curves T t = const., we 

 have a loss or gain of horizontal transport of 100,000 tons per second. The areas 

 into which the bands of flow are divided by the curves of equal transport will thus 

 represent a vertical transport of 100,000 tons per second through the upper limiting 

 surface of the sheet. This transport is directed upward or downward according 



Fig. 105. Areas of equal vertical mass-transport through a surface where pressure is one unit smaller 

 than at the ground. U. S. A., 1905, Nov. 28, 8 a. m. 



as the numbers on the curves T, = const, decrease or increase as we proceed in 

 the direction of motion along the tubes. The triangular areas which surround the 

 point and the lines of convergence represent the same vertical transport as the 

 others. As small areas indicate intense vertical motion, we see that we have a 

 powerful ascending motion near the point of convergence, especially on its northern 

 side and along the lines of convergence. But areas of descending motion also occur 

 even very near the point of convergence and between two of the lines of convergence. 

 If we multiply the pressure of i decibar, which defines the sheet, by o. i we get 

 a sheet which has the thickness of about 75 meters. The tubes of flow will have 

 a transport of 50,000 tons per second at the wall C, and the areas will represent a 

 vertical transport of 10,000 tons per second through a surface having the approxi- 



