REPORT OF THE SECRETARY. 29 



About twenty years ago this industrious meteorologist presented 

 to the American Philosophical Society an investigation of the first of 

 the above-mentioned storms, which extended from the Gulf of Mexico 

 to an unknown distance to the north. The area covered by the ob- 

 servations, and to which consequently the investigation was confined, 

 included only the southern part of the storm, and therefore the au- 

 thor regarded the results he had obtained, though of sufficient interest 

 to warrant publication, as not entirely satisfactory. Having since 

 obtained additional information, and adopted with success in the 

 study of similar storms a method of investigation which consists in 

 representing the disturbances of the atmosphere by lines and colors 

 on charts, he concluded to review his former labors, and to publish 

 all his results illustrated by a series of colored maps, which he is now 

 enabled to do through the provision made for this purpose by the 

 Smithsonian Institution. 



The author first presents a summary of the observations of the 

 barometer at each of the American stations from which information 

 in regard to the indications of this instrument was derived. The 

 average height of the barometer at each of the stations is given, and 

 the fluctuations from this height during the storm, as well as imme- 

 diately before and after it. With these data a series of lines is drawn 

 on five charts, exhibiting the progress of the storm for as many suc- 

 cessive periods, namely, for December 19, at 8 o'clock p. m.; Decem- 

 ber 20, at 8 a. m. and 8 p. m.; December 21, at 8 a. m. and 8 p. m. 

 On each chart is drawn a line indicating the places of mean pressure 

 of the atmosphere, or those where the pressure is in a normal con- 

 dition, also a line indicating two-tenths of an inch of mercury above 

 the mean, &c. 



In examining these lines on each map, it is apparent that there 

 exists a large area over which the barometer was below its mean 

 height, which on the evening of the 20th of December extended 980 

 miles from west to east. On the morning of December 21 it extended 

 770 miles, and on the evening of the 21st it had become reduced to 

 COO miles in the same direction. It is evident, also, that toward the 

 north the limit of low barometer extended much beyond the map, 

 and, since the lowest point was found- at Quebec, it is inferred that it 

 extended as far north as it did south of this point, and would, there- 

 fore, be on the 21st of December at least 3,000 miles in length from 

 north to south. The area, therefore, of least pressure was in the 



