66 THE VOYAGE OF H.M.S. CHALLENGER. 



further developed and extended, and in each case the isobars show a pressure of 29 '60 

 inches. South-westerly winds have increased in frequency and force over western 

 Europe, and in the west of America to the north of the Columbia Eiver ; whilst north- 

 westerly winds have equally increased over Canada and the more northern portion of 

 the United States, and over the east of Asia. In western Europe the rainfall is very 

 largely increased, the maximum monthly fall for the year occurring in Norway, the 

 British Islands, with the exception of the strictly western districts, and over large 

 portions of France and Spain. On the coast stations of British Columbia the rainfall 

 is also heavy, rising to 15 '01 inches at Fort Simpson on a mean of the two years 

 1887-88, and at Sitka the mean is 1T83 inches. On the other hand, the north- 

 westerly winds have largely increased the cold and dryness of the climates of the 

 eastern regions of Asia and North America. The low summer pressure of India is 

 now represented by a shallow depression, having its centre in the Bay of Bengal, where 

 the lowest isobar indicates a pressure of 29"80 inches. The winds accompanying the 

 depression of this transition month from the summer to the winter monsoon are 

 extremely interesting, and the differences shown by the prevailing winds of the Bay of 

 Bengal and the Arabian Sea are very striking. 



Low pressure systems also occur in Central Africa, in the north of South America, 

 and thence westward through the Pacific to longitude 140° W. ; and again in the 

 Pacific between New Guinea and the Sandwich Islands. There is also a slight but 

 wide- spread depression over the Mediterranean, and the influence of the higher 

 temperature maintained by the Black and Caspian Seas is well seen in the deformation 

 of the isobars in their neighbourhood. 



November. — In the central parts of the Arctic regions the isothermal of -15° encloses 

 an extensive area, and the isothermals droop in lower latitudes through eastern Siberia, 

 and in North America in the direction of Lake Winnipeg. In Siberia, a centre of 

 still lower temperature is now formed round Werkojansk, where temperature has fallen 

 to -39°'5, the mean of November being thus 38°"9 lower than that of October. The 

 most southerly position of a mean temperature of 32° is to the south of Wladistok, 

 about lat. 42° N. The protrusion northwards of high temperatures along the west 

 of Norway, and the protrusion southward of low temperatures through the centre 

 of Scandinavia, are among the most striking contrasts in the distribution of the 

 temperature in November. The higher temperature of the Eed Sea, the curves of 

 the isothermals in America from Mexico to the head waters of the Missouri, the 

 irregular courses of the isothermals over the seas of southern Europe, the courses of the 

 isothermals of 45°, 40°, 35°, 30°, and 25° over Europe as compared with the contours of 

 the Continent, and the distribution of temperature in India, are prominent features in 

 the climatologies of the month. 



The highest isothermals are 95° in the north of Australia, 90° in South Africa, 

 and 85° in South America and Central America. Owing to the distribution of the 



