CONTRIBUTIONS TO METEOROLOGY. 

 Table XVII. — Comparison of storm paths icith wind directions. 



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50. From this table it is seen that at all of the stations (except Pembina, Saint Paul, and La 

 Cros.se) the average wind of winter blows towards a point somewhat south of cast, and at the more 

 western stations this direction is more than 30° south of east. It will also be seen that at the 

 most western stations the average movement of storm centers is towards a point more than 15° 

 south of east, but at the most eastern stations the direction is a little north of east. Comparing 

 these numbers, we find that at the most western stations the average course of storm centers is 

 from 10° to 20° more northerly than the course of the wind, while at the three stations above 

 mentioned the average course of storm centers is decidedly less northerly than the course of the 

 wind. The main result of this comparison is similar to that derived from observations on the 

 Atlantic Ocean, viz, that there is not a rigorous correspondence between the average direction of 

 the movement of storm centers and the progress of the wind, but that in some regions the average 

 course of storm centers is more northerly than that of the wind, and in some I'egions it is more 

 southerly. 



51. It frequently happens that the southward motion of storm centers, which is shown by the 

 preceding table in the valley of the Missouri River, is much more decided, and extends to much 

 lower latitudes. Every year cases occur in which this southward motion extends to the parallel 

 of 30°, and occasionally it extends to the parallel of 25°. Table XVIII shows cases in which storms 

 have advanced towards the southeast as far as the parallel of 28°. The arrangement is similar to 

 that of Table VIII. The first six columns describe each storm as long as its course continued 

 southeasterly ; the seventli column shows the highest pressure prevailing at any place within the 

 limits of the United States on the north side of the low area, and the last column gives some 

 indication of the subsequent course of each storm. The tracks of these storms are all delineated 

 on Plate XIII, and are designated by the same numbers as in the table. 



52. We see from this table that the average velocity of these storms while pursuing their course 

 towiirds the southeast was 25 miles per hour, which is somewhat less than the average velocity 

 of storms for the United States. In forming this average I have omitted No. 18, whose path is 

 very imperfectly known. The lowest latitude attained by any of these storms was 23°, and in 

 only four cases did the low center reach the parallel of 25°. In thirteen cases the storm center, 

 after completing its course towards the southeast, changed its course and proceeded towards the 

 north or northeast. In six of the remaining cases the intensity of the storm declined in advancing 

 southward, and they apparently became extinct soon after the dates given in the table. The 

 same was probably true in the four remaining cases, but the observations are not sufficient to 

 establish this with certainty. 



The low area, No. 12, was quite peculiar, having pursued a path almost directly ojjposite to that 

 of ordinary storms. During the afternoon of August 20, 1878, there was an area of low pressure 

 (29.75) over West Virginia, being part of a greater depression, whose center was over Newfound- 

 land, and there was a slight tendency to the formation of an independent system of circulating 

 winds. Owing to a slight increase of pressure on the north side the center of this low area was 

 crowded southward, and in the afternoon of August 21 the low area (29.78) was pretty distinctly 

 marked, and showed a feeble system of circulating winds. At 7.35 A. m., August 22, this low cen- 

 ter had been crowded south to latitude 30°, the greatest observed depression being now 29.88. By 

 the evening of August 22 the pressure at the center had increased to 29.95, and after this the low 



