REPORT ON ATMOSPHERIC CIRCULATION. 71 



As Iceland was on the north-east side of the patch of high pressure overspreading 

 the north of the Atlantic, northerly winds prevailed there, and temperature consequently 

 fell 7°'2 below the mean, presenting thus a marked contrast to the high temperature in 

 West Greenland in the same month. In Europe, the region of lowest pressure occupied 

 the southern shores of the North Sea, thence extending, though in a diminished degree, 

 to south-eastward. It inevitably followed that over all western Europe winds were N.E., 

 N., and in the south-west of Europe, W. ; and everywhere from the North Cape to the 

 north of Italy temperature was below the normal, in some places greatly so, the defect 

 being 10°'4 in the south of Norway and 12 0, 2 in the south of Scotland. 



On the other hand, on the east side of this area of low pressure winds were 

 southerly, and consequently temperature was high. In some parts of Russia it rose 

 to 15 o- above the mean, and over the greater part of European Russia the excess 

 exceeded 9°-0. This region of high temperature extended eastwards into Siberia as far 

 as the Irtish, being quite coterminous with the western half of the anticyclonic region 

 of high pressure which covered central Siberia. But over the eastern half of this 

 Siberian anticyclone northerly winds prevailed, with the necessary accompaniment of 

 low temperature over the whole of eastern Asia, the defect being G° - 8 at Nertchinsk 

 and 9°'0 at Chabarowka on the lower Amur. 



Here again, as in America, Greenland, and Iceland, places with the atmospheric 

 pressure equally high presented the strongest contrasts of temperature, just as they 

 happened to be situated on the eastern or western sides of the anticyclones prevailing 

 at the time. Thus at Bogoslovsk, on the Ural Mountains, pressure was 0-210 inch, 

 and at Nertchinsk 0-154 inch, above the normals; but Bogoslovsk, on the west side of 

 this anticyclonic region, had its temperature 15° - above, whilst at Nertchinsk, on the 

 east side, it was 6° "8 below the average. At the former place winds were southerly, 

 but at the latter northerly. 



In this season the mean pressure falls to the annual minimum in Australia, but 

 during December 1878 the usually low pressure was still further diminished. Pressure 

 at this time of the year also falls to the minimum in the North Pacific and in the 

 North Atlantic, and, as has been stated, the low pressure of these regions was also 

 still further diminished. But in the case of the Atlantic, it was accompanied with a 

 most important difference ; the centre of least pressure, usually located to the south- 

 west of Iceland, was removed some hundreds of miles to south-east, and a most 

 unwonted development of extraordinarily high pressure appeared to the northward, 

 overspreading the extensive region of Baffin's Bay, Greenland, Iceland, Faro, and 

 Shetland. Now it was to this region of high pressure, in its relations to the low- 

 pressure region to the south-east of it, that the extreme severity of the weather over 

 the British Islands at the time was due. It is remarkable that with the exception ot 

 the high-pressure area about Greenland, and the displacement of the low-pressure area 



