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



Atlantic and Pacific immediately to the west of the continents, to the west of Australia, 

 and other satellite anticyclones in Australia, South Africa, and South America. The 

 best marked of these is the one in the North Pacific, where the mean pressure is 30*30 

 inches, and the least in Australia, where the mean is only 30*05 inches; but even in 

 this last case the winds afford a well-defined illustration of the an ticy clonic weather 

 conditions in this part of the globe at this season, inasmuch as they blow outward upon 

 the sea on all coasts. 



One of the most sharply marked cyclonic areas of low pressure which occurs in this 

 month is in south-western Asia, where pressure falls to a mean of 29 "45 inches, and 

 the barometric gradient from the Straits of Ormuz to the Caspian Sea is one of the 

 steepest mean gradients that occur anywhere at any season. The next best marked 

 cyclonic region is that in North America, and others much less marked appear between 

 Iceland and Labrador, in Scandinavia, Spain, and in the eastern equatorial region of the 

 Pacific. It is also to be noted that the equatorial low pressure between the two 

 anticyclonic regions of the Atlantic is now less marked and greatly contracted in 

 breadth. 



July. — This is the typical month of the summer of the northern and of the winter 

 of the southern hemisphere. The three regions in Asia, Africa, and North America, 

 enclosed in June with the isothermal of 95°, and marking off the hottest regions of the 

 globe in that month, cover now a wider extent, and include maximum temperatures a 

 few degrees higher, indicating absolutely the highest mean temperatures that occur 

 anywhere or at any season. 



Among the most interesting features of the climates of restricted regions shown by 

 the isothermals may be enumerated the relatively low temperature of Nova Scotia, the 

 coast of Morocco, Burmah, and Victoria in Australia ; and the relatively high tempera- 

 ture of the eastern division of India sheltered from the summer monsoon, and the 

 inland regions of Scandinavia, Spain, Italy, and Greece. The influence of the Eed Sea 

 in these months is conspicuously seen in maintaining a low temperature, and thereby 

 breaking the continuity between Asia and Africa of the isothermals of 90° and 95°. The 

 crowding together of the lines in California and between the Bay of Biscay to the south 

 of Algiers is very remarkable. 



The more important changes of the distribution of the pressure are an increase over 

 the southern hemisphere generally, with very slight exceptions in South Africa, New 

 Zealand, and the south of South America ; India, except the north-west ; Japan ; a 

 patch of Europe, extending from the north of Spain to Hungary ; the south-western 

 half of the North Atlantic, and the continental portions of North America from the Gulf 

 of Mexico north-westward to lat. 55°. Elsewhere pressure has diminished, but particu- 

 larly over Asia and Europe, except the regions mentioned above, the northern half of 

 the North Atlantic, and nearly the whole of British America. 



