The Great Storm of March- 11-U, 1888. 43 



As stated above, the isobars about an area of low barometer are 

 somewhat circular in form ; more strictly speaking, they are 

 somewhat oval or elliptical in shape, and the more elongated the 

 north and south axis of this ellipse, the greater the resulting 

 changes of temperature, because, as it moves along its broad 

 path toward the Atlantic, the indraught, or suction, is felt in fron\ 

 far down toward the tropics, and in rear far to the northward, 

 beyond the territorial limits of the United States. 



Similarly with regard to the general movement of areas of 

 high barometer, certain laws of motion have been clearly estab- 

 lished by means of studies of the daily international chai'ts; 

 instead of a motion toward east-northeast, these areas when 

 north of the 40th parallel, have in general a motion towards 

 east-southeast, and as a rule move more rapidly and with greater 

 momentum than " lows," so that they may be said to have the 

 right of way, when the tracks of two such systems converge or 

 intersect. These laws, or at least that relating to the Great 

 Lake storm track, as it may be called, soon become evident to 

 anyone who watches the "weather map from day to day, upon 

 which are charted the systems of low and high barometer as they 

 follow one another across the contment, bringing each its charac- 

 teristic weather. 



March 11th, 7 A. M. 



The first of the accompanying weather charts indicates graphi- 

 cally the meteorological conditions over the wide area charted, 

 comprising about 3,000,000 square miles, of which one-third is 

 land and two-thirds water. Over the land there is a long line, or 

 trough, of low barometer, extending from the west coast of 

 Florida up past the eastern shore of Lake Huron, and far north- 

 ward toward the southern limits of Hudson Bay. In front of 

 this advancing line the prevailing winds are southeasterly, and 

 the warm moist air drawn up from southern latitudes spreads a 

 warm wave along the coast, with generally cloudy weather and 

 heavy rains, especially south of Hatteras ; the Signal Service 

 observer at Pensacola, for example, reports the heavy rain-fall of 

 4,05 inches on the 10th, About midway of this trough of low 

 barometer there is a long narrow region of light variable winds ; 

 of rapid changes in meteorological conditions ; calms, shifts of 

 wind, intervals of clearing weather ; then overcast again, with 

 cooler and fresh northwesterly winds, increasing to a gale. The 



