THE SMITHSONIAN INSTITUTION. 203 



extending across the country from Florida to Texas, may flow north- 

 ward and gradually diffuse itself as a surface current over the valley 

 of the Mississippi and the seaboard States. The sun heating the earth 

 more at the north, during the longer days, assists in the propulsion of 

 this current. The higher portions of this lower current are in contact 

 with the under surface of the cold upper current from the west, and in 

 the mingling of the tv^^o the moisture of the former is precipitated into 

 clouds or rain. In some cases the lower current may thus be gradually 

 absorbed into the upper one, and this action may take place over a con- 

 siderable portion of the country, producing an extended cloudiness and 

 perhaps a general fall of rain without violent atmospheric disturbance. 



In winter, the propulsion of the southerly winds is not favored by the 

 heat of the sun; at this season, therefore, they do not extend to so 

 great a breadth as in summer, and only flow over the northern regions in 

 streams, forming narrow belts of warm and moist air, to which we have 

 just adverted. This warm current is often bounded by cold air, on the 

 east and the west. The cold air on both sides is' drifting from west to 

 east, the warm current between (flowing from south and southwest) is 

 also carried laterally to the east; and hence, the moist and warm 

 weather of winter has an apparent motion from west to cast. 



Our inquiries relative to this point lead us to believe that the south 

 and southwest winds in winter may begin to blow over Texas and the 

 high ground a little to the east of the slopes of the Rocky Mountains, 

 and cause a rise of temperature to the west of the Mississippi, when 

 the northwest wind is still blowing dry, cold, and clear, over the whole 

 of the middle and eastern States. 



This, however, does not continue long; the west, northwest, and 

 north winds soon descend between the western edge of the southern 

 current and the mountains, and gradually force the former eastwards. 

 On these occasions the north or northwest wind is the predominant one, 

 which, rushing along the slopes of the mountains to the south, forms 

 tlie well known northers from Vera Cruz to Cuba. According to this 

 view, the norther should be felt sooner at the former place than at the 

 latter. This much is certain, that almost every cold spell of weather 

 which is experienced in the United States during winter is propagated 

 to Cuba in the form of a norther, which, though the thermometer 

 seldom sinks it below 55° at sunrise, is disagreeably felt by the inhabit- 

 ants of the island.* 



* Since this lecture was written, I have had occasion to examine an niteresting series of 

 "Queries and Strictures," by Dr. Hare, in regard to Mr. Espy's Meteorological Report. 

 The view which we have taken of the northers in the Gulf of Mexico will, as far as it goes, 

 answer in the affirmative Dr. Hare's 20th query, page 5 : 



" Whether northers are not consequent to the displacement of the warmer air lying on tho 

 Gulf by the colder air of the territory of the^United States north or northeast (northwest.') of 

 the Gulf, to whatever cause that displacement may be due.'" 



Among the number of interesting points suggested by Dr. Hare for discussion, an answer 

 to the following queries we consider would contribute much to the advancement of the meteor- 

 ology of the United States ; 



" 5th. Wherefore, in one of Mr. Espy's generalizations, he alleges that storms travel from 

 west towards the east during the five wmter months, instead of alleging that they travel from 

 northwest to southeast, consistently with the observations of Loomis, above mentioned?" 



" 7th. Whether there is not another distinct kind of storm, long known and universally 

 recognised as the ' northeaster,' or ' northeastern gale,' which has been distinguished from 

 the southeaster, so called by its direction, its longer endurance, lesser violence, and by its 

 not being usually followed, after a brief lull, by a northwester, nor any violent wind in a 

 direction directly o])posite to that in which it blew at the beginning of the storm.'" 



