§ 241-243. THE ATMOSPHERE. 39 



at the bottom of freezing water, an arrangement whicli subserves, 

 in manifold ways, wise and beneficent purposes. So, too, wben 

 we discern in tlie upper sky (§ 234) currents of wind arranged in 

 strata one above the other, and running hither and thither in dif- 

 ferent directions, may we not say that we can here recognize also 

 at least one of the foreordained offices of these upper winds? 

 That by sending down fresh air and taking up foul, they assist 

 in maintaining the world in that state in which it was made and 

 for which it is designed — " a habitation fit for man?" 



241. The phenomenon of cold belts or bands is often observed 

 The effect of do;vn- in the United States, and I suppose in other parts of 

 producing cold. thc world also ; and here in these downward cur- 

 rents we have the explanation and the cause of sudden and severe 

 local spells of cold. These belts generally lie east and west rath- 

 er than north and south, and we have often much colder weather 

 in them than we have even several degrees to the north of them. 

 The conditions required for one of these "cold snaps" appear to 

 be a north or northwest wind of considerable breadth from west 

 to east. As it goes to the south, its tendency is, if it reach high 

 enough, to bring down cold air from above in the manner of the 

 trade-winds (§ 238) ; and when the air thus brought down 

 chances to be, as it often is, dry and cold, we have the phenome- 

 non of a cold belt, with warmer weather both to the north and the 

 south of it. AVhile I write the thermometer is —4° in Mississip- 

 pi, lat. 32°, and they are having colder weather there than we have 

 either in Washington or Cincinnati, 7° farther to the north. 



242. The winter "northers" of Texas sometimes bring down the 

 The winter northers ^^Id air there with tcrrific effect. These bitter cold 

 of Texas. wiuds are very severe at Nueces, in the coast coun- 

 try, or the southwest corner of Texas bordering the Gulf of 

 Mexico, lat. 27°.5. They are often felt to the west in Mexico, 

 but rarely in eastern or northern Texas. The fact that they are 

 not known in northern Texas goes to show that the cold they 

 bring is not translated by the surface winds from the north. 



243. A correspondent in Kueces, lat. 27° 36' K, long. 97° 27' 

 Their severe cold. W., has dcscribcd thcsc wiuds there during the win- 

 ter of 1859-60. They prevail from November to March, and com- 

 mence with the thermometer about 80° or 85°. A calm ensues on 

 the coast; black clouds roll up from the north; the wind is heard 



