United States Weather ^faps and other sources. 9 



drawn so as to show the tracks of storms from day to day, I 

 placed in one column the latitudes of all the storm centers 

 between the meridians of 60° and 45° W. from Paris ; in a sec- 



olumnl 

 30° W., and s 



average of all the latitudes in each of the columns. The result 

 is shown in columns third and fourth of the preceding table, 

 and the path thus determined is traced on the accompanying 

 chart This path passes over Dublin, and will be seen to form 

 a natural continuation of the track deduced from the Ameri- 

 can observations. This result is doubtless accidental and is due 

 to the fact that near the American coast the observations from 

 which the Paris maps were constructed were derived from a re- 

 gion extending but little north of the stations of the United 

 States Signal Service, If the Paris maps had included obser- 

 vations from Labrador and Greenland the average track of the 

 storms represented would have been more northerly than it 



I proceeded in a similar manner with Hoffmeyer's charts ex- 

 cept that the meridians were selected at intervals of 10°, and 

 the results are shown in columns fifth and sixth. The path 

 thus determined lies several degrees north of that previously 

 determiued, and this arises from the fact that the maps exhibit 

 the results of observations made in Greenland and Iceland as 

 well as from more southern latitudes. In order to deduce an 

 average result from the French and Danish maps I have com- 

 bined them in a single series, and the result is' shown in col- 

 umns seventh and eighth of the preceding table. The path 

 thus determined is traced on the accompanying chart and 

 passes through the northern extremity of Scotland. 



In order to show the connection between storm paths and the 

 mean height of the barometer, I have drawn upon the same 

 chart two other barometric lines. The mean height of the ba- 

 rometer at the level of the sea varies with the latitude of the 

 place. On the Atlantic ocean at the equator the mean height 

 of the barometer is about thirty inches. If from this point we 

 travel northward the pressure increases, and in latitude 30° be- 

 comes about 80*2 inches. Thence the pressure diminishes to 

 29-6 inches near latitude 70°, from which point the pressure 

 slightly increases as we advance northward. A somewhat sim- 

 ilar result takes place in going from the equator to the North 

 Pole upon any meridian, but the maximum pressure is not the 

 same under all meridians, and the same is true of the minimum 

 pressure. The undulating line near the bottom of the accom- 

 panying chart shows the line of the greatest mean pressure 

 varying on different meridians from^ about 30 ihches to 

 30-2 inches. The undulating line near the top of the chart 



