abstracts: meteorology 79 



quently tend to slide down toward the pole. Hence there are two belts 

 of high barometric pressure surrounding the earth; one at about 32° S, 

 and the other about the same latitude north. Both are well marked on 

 the oceans, but, owing to great temperature variations, are practically 

 obliterated over continents. 



But even on the oceans the belts are not uniform. The northern 

 belt has one region of maximum pressure, with closed isobars, just west 

 of southern California, and another in the eastern Atlantic. The south- 

 ern belt has three regions of maximum pressure; one just west of Chile, 

 another west of southern Africa, and a third west of Australia. Each 

 of these five regions of maximum pressure is essentially permanent, 

 accompanied by fair weather, and surrounded by gentle anticyclonic 

 winds. 



At each of the five places of maximum barometric pressure, but no- 

 where else, the belts of high pressure are crossed by cold ocean currents. 

 These pressure maxima, therefore, are due to the combined influence of 

 the mechanical action of the oppositely directed winds north and south 

 of them and to the low temperature of the cold ocean currents, and are 

 located where the sum of the two influences has its maximum values. 



The original paper contains several explanatory figures. W. J. H. 



METEOROLOGY. — On the relation between atmospheric pressure and 

 wind. J. W. Sandstrom. Bulletin of the Mount Weather Obser- 

 vatory, 3: 275-303. 1911. 



A difference in barometric pressure between two neighboring places 

 at the same level necessarily must start the wind blowing from the place 

 of higher towards the place of lower pressure. But the direction of 

 flow is modified by the rotation of the earth, and by frictional resistance. 

 There are, then, three forces acting on a moving mass of air. A gravita- 

 tional force proportional to and in the direction of the barometric gra- 

 dient, (2) a force, clockwise in the northern hemisphere, at right angles 

 to the instantaneous direction of the wind and proportional to the sine 

 of the latitude, (3) a frictional resistance numerically equal and opposite 

 in direction to the resultant of the other two. 



On applying these facts to special cases the friction is found to be 

 divisible into two portions, one of which is that of the wind on the sur- 

 face of the earth, and the other that between the wind and the upper 

 currents of air, which usually differ from the surface winds both in direc- 

 tion and speed. The author also shows how these forces may so com- 

 bine as to cause the wind to follow a sinuous path. 



The original paper is abundantly illustrated by meteorological charts 

 of northern Europe. W. J. Humphreys. 



