REPORT ON ATMOSPHERIC CIRCULATION. 63 



The stations are separated into two distinct groups by a line made to pass in a 

 north and south direction through the centre of the low-pressure area. To the west of 

 the line the summer rainfall is either nil or small, whereas to the east of it the rainfall 

 reaches the annual maximum in this season. The influence of this low pressure 

 is to augment the summer rainfall, at least as far eastward as the Mississippi. Farther 

 north on Hudson's Bay and the N.-W. Territories of Canada the summer rainfall is for 

 the same reason also large, the amount being in a great degree to be traced to the 

 large evaporation from Hudson's Bay conveyed by the prevailing winds southwards 

 and distributed over the Territories. The rapid increase of the rainfall on the seaboard 

 from the Columbia River northwards is remarkable, the amounts for July being 

 1*16 inch at Astoria ; 2'81 inches at Tatoosh Island, near Cape Flattery; 3'56 inches 

 at New "Westminster ; and 4 "3 1 inches at Fort Simpson, to the north-east of Queen 

 Charlotte Island. At all coast stations to the north of San Francisco the winter rain- 

 fall is very large. The greatest falls occur at Tatoosh Island, Fort Simpson, and Astoria, 

 and the heavy rains set in as early as September. 



August. — The declining influence of the sun is now decidedly felt in the higher 

 latitudes and in the drier continental climates. The temperature of a considerable 

 portion of the Arctic regions has now fallen below the freezing point. At Barnaul, in 

 Siberia, temperature falls from 68°'6 in July to 62°"5 in August, and at Werkojansk, 

 where the greatest known cold is recorded in the winter, the figures are for July 5 8° "6 

 and August 48°'7. 



On the other hand, the temperature of the oceans, as well as in many strictly 

 insular situations of the northern hemisphere, rises to the annual maximum in this 

 month. At Astrabad, on the Caspian Sea, the means are for July 81°'7 and August 

 83°-4, at Nagasaki 77°'7 and 79°-8, and at Bellisle 48°-8 and 50°-9/ The influence 

 of extensive water surfaces in maintaining a higher temperature towards the close of 

 summer is well illustrated by the air temperatures of the Atlantic and Bed Sea. 



The high temperature of the Atlantic on the one hand, and the upwelling of the 

 cold deep water to the surface off the north-west coast of Morocco on the other, result 

 in the singular positions of the August isothermals of that ocean. Similar low 

 temperatures are also seen in each case where the four great anticyclonic areas of high 

 pressure in the Pacific and Atlantic press on the continents, the lowering influence 

 being increased by the prevailing winds passing into lower latitudes. 



The changes in the distribution of the pressure are an increase over the whole of 

 Asia and Europe, except the countries in the south-west of the latter continent, the 

 increase being greater in those regions where the most marked fall in the temperature 

 is proceeding ; over North America, except the extreme western and extreme southern 

 regions ; and in South America, to the south of the Argentine Republic. On the other 

 hand, pressure has fallen over France, Italy, Spain, and Portugal ; over the Atlantic, 



