METEOROLOGY. 341 



incr.ts and changes of depressions of storm centers on the ocean arc 

 much more irregular than over the North American continent. Th(^ 

 main storm track passes from Wisconsin eastward to Newfoundland, 

 thence northeast to the North Cai)e; outside of this track, areas of 

 great storm frequency are found in Davis Straits and Northern Ger 

 many. (Z. 0. G. M., xvii, 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 l.s76 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 dei»ressiou, and equal average 

 barometric <leparture of the pressures at storm centers frotn 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 Kui()i)e, it being 100 

 myriameters per day in the United States and only 04 myriameters in 

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

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

 winter, which, as he says, is an important indi(;ation of the fact that 

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

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

 myriameters in thirty cases daring the five 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. i¥., xvii, p. i97.) 



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 per cent., autumn 20, winter 30, and spring 24 i)er cent. 

 The mean pressure 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 ceu 

 tral dei)ression 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 the southwest in January, February, 

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

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

 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. (i>. M. 

 Z., I, 320.) 



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

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

 weight than the surrouudiug masses of atmosphere j the movement of 



