DESCRIPTION OP MAPS AND DIAGRAMS. 753 



States, and from N. W. on the Atlantic Coast of Europe in summer. Similar monsoon influences 

 are at work on the coast of the White Sea and Arctic Ocean. In the real monsoon regions the 

 deflecting forces are very powerful. 



The mode by which these forces are ascertained is explained in the introduction to this work, and 

 also fully illustrated in Plate 2G. 



As the opposition of these forces, however varied tiiey may be in their directions and intensities, 

 must ever represent a state of e.vact mechanical equilibrium, some apparently abnormal cases found 

 on the ocean, and mostly south of the equator, must bje accounted for ; that they be not attributed 

 to erroneous computation. For instance, Zone 24, serial numbers 10 to 21 et seq., and preceding 

 zones, in reference to which foot-notes have usually been appended to the respective pages of the 

 Tables. They are to be explained by the fact that the observations in those localities were not 

 numerous enough to be taken as the basis of a reliable annual resultant, and, therefore, the monsoon 

 influences were obtained by comparing the separate seasons — not with the meagre yearly resultant 

 that they would have afforded — but with an annual resultant that was obtained by combining all the 

 observations taken on that ocean, and within the limits of the zone. 



PLATE 11. 



Monsoon Influences in the United States. 



[See Explanation of Plate 10.] 



The remarkable constancy of the winds between the Apallachian range and the Mississippi, and 

 34° and 42° N. lat., is especially to be noticed here. Hence the monsoon influences are extremely 

 weak. The most powerful monsoon influences are seen in Texas, the region of the United States 

 which is most like Eastern Asia in the course of its winds. 



PLATE 12. 



Monsoon Influences in Europe. 



In winter a monsoon influence from the S. E. is seen in Europe; it is a reaction of the high pres- 

 sure in the interior of the continent. In summer, on the contrary, except in a part of the Mediterranean 

 region, the monsoon influences are from the west. 



PLATE 13. 



Annual Mean Direction op the Winds in the United States, showing that calculated 

 WHEN the Velocity is taken into account in comparison with that for Time only. 



The first is expressed by broken arrows, the last by full arrows. It will be seen that the mean 

 direction varies but little, if the velocity is taken into account, from that calculated from the time 

 only. Generally in the first case the ratio of resultant is somewhat greater (the arrows longer). For 

 a more extended view of this topic, compare with this map the diagrams found in Plate 25, and also 

 the introduction to the Velocity Tables, in Series C. 



PLATE 14. 



Maps of Isobars or Lines of Equal Atmospheric Pressure at Sea-Level for the Tear, 



January and July. 



These maps are inserted from the treatise of Buchan, "Mean Pressure and Prevailing Winds of 

 the Globe," published in the Transactions of the Royal Society of Edinburgh, vol. xxv., which was 

 tlie first attempt to do for the pressure of the air what Humboldt and Dove had done for temperature. 



95 July, 1875. 



