SKETCH OF ELI AS LOOMIS. 409 



December 20, 1836 — concerning wliicli, it occurring on one of tlie 

 term days which Sir John Herschel had suggested as days for a 

 general system of observations, he was able to collect data from 

 all parts of the United States and some stations in Canada. His 

 discussion of this storm, in a paper read before the American 

 Philosophical Society in March, 1840, was. Prof. Newton says, 

 " probably more complete than that of any previous one, and the 

 methods which he employed were better fitted to elicit the truth 

 than any earlier methods. . . . The results which he was able to 

 secure did not sustain either of the two rival theories, but rather 

 tended to prove some features in each of them." The studies 

 were continued with the examination of the track of a second 

 tornado in February, 1842, which proved to be a part of a general 

 storm, and of another great storm that occurred in the same 

 month. The paper embodying the results of these observations, 

 which was read at the centennial meeting of the American Philo- 

 sophical Society, in May, ]843, is remarkable for ha\dng intro- 

 duced a new method of investigation. The delineations of 

 storms previous to the composition of this paper had attempted 

 no more than to indicate the progress of the center of minimum 

 pressure by lines drawn from point to point, to which a few lines 

 were added to show certain facts about the movements of the air. 

 " In the discussion of the storms of 1842, instead of the line of 

 minimum depression of the barometer, Prof. Loomis drew on the 

 map a series of lines of equal barometric pressure, or rather of 

 equal deviations from the normal average pressure for each 

 place. A series of maps representing the storm at successive 

 intervals of twelve hours were thus constructed, upon each of 

 which was drawn a line through all places where the barometer 

 stood at its normal or average height. A second line was drawn 

 through all places where the barometer stood two tenths of an 

 inch below the normal," etc. ; and also for places where the ba- 

 rometer stood above its normal height. " The deviations of the 

 barometric pressure from the normal were thus made prominent, 

 and all other phenomena of the storm were regarded as related to 

 those barometric lines. A series of colors represented respective- 

 ly the places where the sky was clear, where the sky was over- 

 cast, and where rain or snow was falling. A series of lines repre- 

 sented the places at which the temperature was at the normal, or 

 was 10°, 20°, or 30° above the normal or below the normal. Ar- 

 rows of proper direction and length represented the direction and 

 intensity of the winds at the different stations. These successive 

 maps for the three or four days of the storm furnished to the eye 

 all its phenomena in a simple and most effective manner." The 

 introduction of this method, which is the prototype, still but lit- 

 tle improved upon, of the weather charts now in general use, is 



