The American Journal of Science and Arts

had moved southeastward and was central over Cincinnati (bar. 30-44). The temperature throughout this vicinity was 15° below the mean of December. At the same time another center of high pressure appeared near the northern line of Dakota, where the barometer was 30-39, and temperature 25° below the mean. On the morning of the 18th the pressure in Dakota had risen to 30-64, with a temperature 44° below the mean. During the 18th this area of high barometer stretched out towards the southeast, and on the morning of the 19th this high pressure extended, like a ridge, from the north line of Dakota to the Atlantic coast near Cape May, where the pressure was 30:52. The greatest depression of temperature was, however, west of Lake Huron, from which region the cold area extended to the Rocky Mountains. At the same time a storm, proceeding from Texas, advanced towards the northeast, and on the morning of the 20th was central over Lake Ontario (bar. 29-43). By this storm the high pressure of the 19th was crowded towards the northeast, and the temperature rose throughout the storm area; but at the same time a new area of high barometer formed in Dakota (bar. 30-37), and the thermometer sunk 34° below the mean. During the 20th this area of high pressure moved southward, and on the morning of the 21st its center was near lat. 42°, and the pressure had increased to 30-72. The cold had now become very intense, and extended over a vast area, the greatest depression being 41° below the mean, and the area of 30° depression stretched from the Rocky Mountains to Lake Michigan, a distance of 1,500 miles. It extended southward to lat. 38°, and northward beyond the limits of the United States.

On the morning of the 22d an area of low barometer formed near the Rocky Mountains, in Wyoming (bar. 29-60), and the area of high barometer was crowded towards the southeast, being now central over Cincinnati (bar. 30.65). The cold area had increased greatly in extent, advancing southward and eastward. It was most intense at Port Stanley, on Lake Erie, where the depression was 44°; but the area of 20° depression extended from the Gulf of Mexico to Canada, and from New York city westward to long. 97°.

The storm of the 22d advanced eastward, and on the morning of the 23d was central over Lake Huron. At the same time an area of high barometer formed in Dakota and Minnesota (bar. 30-60) accompanied by a very low temperature. At La Crosse the depression was 39° below the mean, and the area of 20° depression extended from Lake Huron to the Rocky Mountains, and from lat. 37° on the south to British America on the north. On the 23d a storm center appeared in Oregon, and on the morning of the 24th the barometer at Portland, Oregon, stood at 29-15. By this storm, the area of high pressure and of low

pressure

temperature, on the east side of the Rocky Mountains, was crowded eastward. On the morning of the 24th the highest pressure was at La Crosse 30.85, and the area of 30-40 extended from long. 100° to New York, and from lat. 34° on the south to British America on the north. On Plate I. are shown the isobars for this date, for each tenth of an inch variation of pressure. The greatest depression of the thermometer was at St. Louis, 45° below the mean, and the area of 20° depression extended from the Gulf of Mexico to British America, and from long. 102° to Nova Scotia. On Plate II are drawn curves, at intervals of 5°, showing how much the temperature at each place was above or below the mean temperature of December. On the morning of the 25th the Oregon storm had crossed the Rocky Mountains, and had crowded the high pressure of the 24th still further eastward. The pressure was now greatest over Lake Ontario, 30-66. The cold area still stretched from Texas to Nova Scotia, the depression being 42° on Lake Ontario, and 32° at Indianola, on the Gulf of Mexico. A storm was now organized over the eastern part of the Gulf of Mexico, accompanied with heavy rain in Florida and along the Atlantic coast, changing to snow as it advanced northward.

On the morning of the 26th the center of this storm was over the Atlantic Ocean near Norfolk, Va. (bar. 29:46). At the same time another area of high barometer had formed over Minnesota (30.92) accompanied by a depression of the thermometer of 31°. On the morning of the 27th this area of high pressure remained nearly unchanged in magnitude and position, but the depression of the thermometer at several places had increased to 37°. During the 27th the high pressure diminished in amount and moved towards the southeast. On the the morning of the 28th the center of high pressure was over Tennessee (30-61) and the greatest depression of the thermometer was 29°. Another storm center had already formed in the northwest, which reached the Mississippi valley on the morning of the 29th, and now at none of the stations west of the Mississippi did the depression of the thermometer exceed 16°.

The accompanying table exhibits the observed changes of temperature from Dec. 16 to Dec. 27. Column second shows the mean temperature of December at the stations named in column first, and the succeeding columns show the difference between the mean temperature of the month and the temperature observed each day at 7b 35m A. M. At this hour the temperature is about 4° below the mean temperature of the day, so that the numbers given in the table should all be increased by about 4° in order to show the depression below the mean temperature at the hour of observation. The depressions mentioned in the preceding description were all copied from this table.

had moved southeastward and was central over Cincinnati (bar. 30-44). The temperature throughout this vicinity was 15° below the mean of December. At the same time another center of high pressure appeared near the northern line of Dakota, where the barometer was 30-39, and temperature 25° below the mean. On the morning of the 18th the pressure in Dakota had risen to 30-64, with a temperature 44° below the mean. During the 18th this area of high barometer stretched out towards the southeast, and on the morning of the 19th this high pressure extended, like a ridge, from the north line of Dakota to the Atlantic coast near Cape May, where the pressure was 30:52. The greatest depression of temperature was, however, west of Lake Huron, from which region the cold area extended to the Rocky Mountains. At the same time a storm, proceeding from Texas, advanced towards the northeast, and on the morning of the 20th was central over Lake Ontario (bar. 29-43). By this storm the high pressure of the 19th was crowded towards the northeast, and the temperature rose throughout the storm area; but at the same time a new area of high barometer formed in Dakota (bar. 30-37), and the thermometer sunk 34° below the mean. During the 20th this area of high pressure moved southward, and on the morning of the 21st its center was near lat. 42°, and the pressure had increased to 30-72. The cold had now become very intense, and extended over a vast area, the greatest depression being 41° below the mean, and the area of 30° depression stretched from the Rocky Mountains to Lake Michigan, a distance of 1,500 miles. It extended southward to lat. 38°, and northward beyond the limits of the United States.

On the morning of the 22d an area of low barometer formed near the Rocky Mountains, in Wyoming (bar. 29-60), and the area of high barometer was crowded towards the southeast, being now central over Cincinnati (bar. 30-65). The cold area had increased greatly in extent, advancing southward and eastward. It was most intense at Port Stanley, on Lake Erie, where the depression was 44°; but the area of 20° depression extended from the Gulf of Mexico to Canada, and from New York city westward to long. 97°.

The storm of the 22d advanced eastward, and on the morning of the 23d was central over Lake Huron. At the same time an area of high barometer formed in Dakota and Minnesota (bar. 30-60) accompanied by a very low temperature. At La Crosse the depression was 39° below the mean, and the area of 20° depression extended from Lake Huron to the Rocky Mountains, and from lat. 37° on the south to British America on the north.

On the 23d a storm center appeared in Oregon, and on the morning of the 24th the barometer at Portland, Oregon, stood at 29.15. By this storm, the area of high pressure and of low

temperature, on the east side of the Rocky Mountains, was crowded eastward. On the morning of the 24th the highest pressure was at La Crosse 30-85, and the area of 30-40 pressure extended from long. 100° to New York, and from lat. 34° on the south to British America on the north. On Plate I. are shown the isobars for this date, for each tenth of an inch variation of pressure. The greatest depression of the thermometer was at St. Louis, 45° below the mean, and the area of 20° depression extended from the Gulf of Mexico to British America, and from long. 102° to Nova Scotia. On Plate II are drawn curves, at intervals of 5, showing how much the temperature at each place was above or below the mean temperature of December. On the morning of the 25th the Oregon storm had crossed the Rocky Mountains, and had crowded the high pressure of the 24th still further eastward. The pressure was now greatest over Lake Ontario, 30-66. The cold area still stretched from Texas to Nova Scotia, the depression being 42° on Lake Ontario, and 32° at Indianola, on the Gulf of Mexico. A storm was now organized over the eastern part of the Gulf of Mexico, accompanied with heavy rain in Florida and along the Atlantic coast, changing to snow as it advanced northward.

On the morning of the 26th the center of this storm was over the Atlantic Ocean near Norfolk, Va. (bar. 29:46). At the same time another area of high barometer had formed over Minnesota (30.92) accompanied by a depression of the thermometer of 31°. On the morning of the 27th this area of high pressure remained nearly unchanged in magnitude and position, but the depression of the thermometer at several places had increased to 37°. During the 27th the high pressure diminished in amount and moved towards the southeast. On the the morning of the 28th the center of high pressure was over Tennessee (3061) and the greatest depression of the thermometer was 29°. Another storm center had already formed in the northwest, which reached the Mississippi valley on the morning of the 29th, and now at none of the stations west of the Mississippi did the depression of the thermometer exceed 16°.

The accompanying table exhibits the observed changes of temperature from Dec. 16 to Dec. 27. Column second shows the mean temperature of December at the stations named in column first, and the succeeding columns show the difference between the mean temperature of the month and the temperature observed each day at 7h 35m A. M. At this hour the temperature is about 4° below the mean temperature of the day, so that the numbers given in the table should all be increased by about 4° in order to show the depression below the mean temperature at the hour of observation. The depressions mentioned in the preceding description were all copied from this table.