METEOROLOGY. 341 



tnetits and changes of depressions of storm centers on the ocean are 

 much more irregular than over the North American continent. The 

 main storm tracli: passes from Wisconsin eastward to Newfoundland, 

 thence northeast to the North Cape; outside of this track, areas of 

 great storm frequency are found in Davis Straits and Northern Ger- 

 many. (Z. 0. G. 71/., XYii, p. 257.) 



284. Dr. J. van Bebber has i)resented an admirable discussion of the 

 relative position, velocity, and intensity of the barometric minima of 

 Europe that have occurred during the years 1S76 to 1880, inclusive. 

 His statistics are presented in the shape of charts showing by curved 

 lines the regions of equal mean velocity : equal maxima of barometric 

 depressions ; equal average barometric de{)ression, and equal average 

 barometric departure of the pressures at storm-centers from the nor- 

 mal pressure. He finds that the mean velocity of i)rogress of a storm - 

 center is greater in the United States than in Europe, it being 100 

 myriameters per day in the United States and only (34 myriameters in 

 Europe. For both countries, however, the annual periodicity is about 

 the same, showing a minimum in August and a maximum during the 

 winter, which, as he says, is an important indication of the fact that 

 some general causes regulate the movement of storm-centers through- 

 out the world. The velocity of the most rapid storms exceeds 150 

 myriameters in thirty cases during the live years; the greatest number 

 of cases of any one velocity is that of 40 to 50 myriameters, for which 

 there were 217 cases. {Z. 0. G. M., xvii, p. l97.) 



285. Leyst has made a study of the storm tracks in European Russia 

 and Western Siberia for the years 1878-'80. He considers only the 

 storms of such a nature as those for which storm signals should issue 

 from the central office at St. Petersburg. Out of 250 cyclones there fall 

 in summer 17 i^er cent., autumn 29, winter 30, and S])ring 24 j)er cent. 

 The mean i^ressure of the central minima is for summer 738 millimeters, 

 for October 732, and for November to March 727. The mean velocity 

 increases as the storms move eastward, and in the summer time the cen 

 tral depression also increases. The velocity of progression is also great- 

 est in January and least in July. The strongest gradients are for sta- 

 tions south and southwest of the centers, and the strongest winds 

 themselves are directed towards ttie southwest in January, February, 

 and June, but to the northwest in March and to the east-northeast 

 in April. When the cyclone comes into such a position that Eussia 

 is in its southwest part, it has already moved further away from the 

 high pressure of Southwest Europe, and also has grown weaker by its 

 passage towards the north or northeast, and for both these reasons the 

 storm in the southwestern quadrant of the cyclone diminishes. (D. M. 

 Z., I, 326.) 



286. M. M oiler, in some remarks on the cause of the movement of 

 barometric depressions, says these depressions are columns of air of less 

 weight than the surrounding masses of atmosphere; the movement of 



