Page:The National geographic magazine, volume 1.djvu/97



Barometer Curves.—As it is only practicable to illustrate graphically the Imrometer records of a few vessels and land stations, the following have been selected as being of special interest; the small circles mark the points of observation:

Barometer Normal.—The barometer normal for the 50-square from latitude 35° to 40° N., longitude 65° to 70° W., assumed for the present purpose as the normal for the entire area, is 29.98, and is indicated by the blue line on the diagram.

The positions of the above-mentioned signal-stations and the tracks of these seven vessels are all indicated in red on the accompanying Track Chart. This diagram should therefore be studied in connection with the chart, in order to form a clear idea of the general eastward movement of the trough of low barometer, and the accompanying rapid deepening of the depression upon reaching the coast.