DISTRIBUTION OF ATMOSPHERIC MOISTURE. 485 



sun from the broad expanse of the Indian Ocean, we find that in the 

 eastern Himalayas the rainfall varies from 200 to 600 inches a year, 

 and that at Mahabaleshwar, where the clouds drift against tlie high 

 ridge that lines the west side of the peninsula, it is 248 inches, but that 

 at Courtallum it is only 40 inches, at Bangalore 35 inches, at Cape 

 Comorin 30 inches, and at Bellary in Mysore 22 inches, which is as 

 low as in any part of England, 



Zone of Periodic Winds without Rain. Outside the zone of 

 periodic winds and rains comes a double belt, one girdling the world 

 in the northern, and the other in the southern hemisphere, the breadth 

 and area of which are greatly modified by local circumstances, within 

 which no rain ever falls. These belts are estimated to include alto- 

 gether an area of 5,000,000 square miles, but it is impossible to make 

 any calculation that is at all precise, because round the tracts that are 

 entirely rainless are regions in which rain falls but rarely, which again 

 pass gradually into the two rainy zones, through countries like South- 

 ern Palestine and the Gangetic plain, which, though usually rainy, are 

 liable at intervals to years of drought. These belts of rainless land 

 near the tropics contain some of the most hopelessly dreary country 

 which the world can show. Beginning with the west of the old con- 

 tinent, we have along the tropic of Cancer in Africa the Sahara or 

 great desert, on the southern border of which the rains cease at 16 

 north latitude, and begin again on the north at 28. Passing farther 

 east, the southern rains cease in the countries on the banks of the Nile 

 between 18 and 19, and the northern begin between 27 and 28. 

 Passing into Asia, there is a great rainless tract in Arabia of which we 

 do not know the exact bounds, and it reaches through Beloochistan 

 over into the delta of the Indus, where it does not cover more than 4 

 of latitude. From this point the rainless zone turns to the northeast 

 and extends to 30 north latitude. Crossing the great Himalayan 

 chain it includes the high table-land of Thibet, but does not appear to 

 reach into the Chinese Empire. In South Africa there is a sandy, des- 

 ert, rainless tract on the north of the Orange River, between 24 and 

 28 south latitude, and a great part of the interior of Australia seems 

 to be nearly or quite rainless. In North America the rainless belt 

 includes the Californian peninsula, and extends round the northern 

 end of the Sierra Madre chain past Chihuahua and Monterey to the 

 shores of the Gulf of Mexico between latitudes 24 and 26. In South 

 America it includes between latitudes 23 and 27 the northern prov- 

 ince of Chili, and, through an extensive low tract in the interior of 

 the continent belonging to the territory of the Argentine Confedera- 

 tion, rain is very unfrequent and small in quantity. 



Zone of Variable Winds and Rains. From about latitude 80 

 on each side of the equator to the poles extends a region of ever- 

 changing and variable winds, and of rain that is irregularly distrib- 

 uted throughout the whole year. Sometimes in these middle lati- 



