DISCUSSION AND ANALYSIS OF WINDS. 733 



The mass of air which is drawn towards the Asiatic continent in summer is so 

 great that the ordinary conditions prevailing over extensive areas of the oceans 

 must be disturbed, as shown on Plates 5 and 14. As there is also a great mass of 

 air drawn towards India and Indo-China, we must here consider Eastern and. 

 Southei'n Asia together. 



The summer monsoon of Asia is a deflection of air already in motion, that is of 

 part of the S. E. trade of the Indian Ocean and part of the N. E. trade of the Pacific 

 Ocean. It is easy to prove this for the Indian Ocean, as the observations there 

 are numerous and well discussed. This is not the case for the Pacific Ocean. Yet 

 seeing a region of high pressure about 30° N. to the E. of China, it is impossible 

 to conceive how the air from above it should not be drawn towards the heated 

 Asiatic continent with its low pressure. Probably at the beginning of the summer 

 monsoon, only the air over the nearest parts of the ocean is drawn towards Asia, 

 and the circle extends as long as the pressure continues to sink over the continent. 



The direction of the winds in summer on the coast of E. Siberia, as well as in 

 China and Japan, shows that they cannot have come from the southern hemisphere, 

 as they otherwise would have a direction from the S. "W. as in India, and not E., 

 S. E., or S. It seems that the air from the Pacific supplies the northern part of 

 this region, from about 25° to 60° N. In Southern China the prevailing winds are 

 already S. W., so that this is probably air from the southern hemisphere. (See 

 Plates 5 and 6.) 



As in summer the Asiatic continent attracts the winds, so, on the contrary, in 

 winter a continuous stream of cold dry air pours out from it towards the surrounding 

 seas. It takes mostly two directions: towards the depression in the northern part 

 of the Pacific as S. W., W., and N. W. winds, and towards the equatorial region as 

 a N. E. On the coast of E. Siberia, in northern China and northern Japan the 

 winds are mostly N. W., in southern Japan and middle China they are N., and 

 near the tropics they have a direction from the N. E. 



The climate of the whole monsoon region is characterized by a gi'eat regularity. 

 This is not only the case in the tropics, but also in the temperate zone. The 

 periodicity of the change of monsoons is the leading feature, taking place at more 

 or less fixed periods, with slight changes from year to year. The N. monsoon of 

 winter is the dry time of the year, the summer or S. monsoon the time of clouds 

 and rain. So, for example, at Pekin the amount of clouds is 2.5 in January and 

 6.3 in July, at Ochotsk, Ajan and Nikolaievsk (Amoor) 2.5 in January and 5.0 in 

 August (an entirely clear sky = 0, an entirely overcast = 10). At Pekin the 

 quantity of rain in July is more than fifty times greater than in January. 



As this distribution of rain and clouds is caused by the monsoon, which brings 

 the dry, cold air of the continent in winter, and the vapor-laden air of the sea in 

 summer, thus causing the above-mentioned periodicity, we have means of judging 

 of the character of the climates of this region even without having observations of 

 winds, Eor a great extent of country, in China and Mantchooria as well as in 

 eastern Siberia, we have no long-continued observations, yet the general character 

 of the climate is known. Thus we must include in the monsoon zone, besides 

 the tropical countries of India and Indo-China, all of China and Japan, Corea, 



