1)4: PHYSICAL GEOGRAPHY OF THE SEA, AND ITS METEOROLOGY. 



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. Tlieir severe cold. — A correspondent in Nueces, lat. 27° 

 36' N., long. 97° 27' W., has described these winds there during 

 the winter of 1859-60: They prevail from November to March, 

 and commence with the thermometer at about 80° or 85°. A 

 calm ensues on the coast ; black clouds roll up from the north ; 

 the wind is heard several minutes before it is felt ; the thermo- 

 meter begins to fall ; the cold norther bursts upon the people, 

 bringing the temperature down to 28°, and sometimes even to 

 25°, before the inhabitants have time to change clothing and 

 make fires. So severe is the cold, so dry the air, that men and 

 cattle have been known to perish in them.* These are the 

 winds which, entering the Gulf and sucking up heat and mois- 

 ture therefrom, still retain enough of strength to make them- 

 selves terrible to mariners — they are the far-famed northers of 

 Vera Cruz. 



244. " Cold Snaps.'" — The temperature of the atmosphere at 

 the height of three or four miles is variable — observations and 

 balloonists tell us so. Air may be brought below the normal 

 temperature due the height at which it may be, by radiation 

 and other processes. It may also be raised above that normal 

 temperature by the setting free there of the latent heat of vapour 

 or by the action of the solar ray upon the cloud stratum. AVhen 

 this upper air is brought to the surface in this abnormal con- 

 dition, the people of the district upon which it descends find 

 themselves in a " cold snap" or "hot term," as the case may be. 



245. Anemometers to determine the inclination oftheimnd ivanted. — 

 That our climates, especially the continental, are affected by, 

 and that many of the changes in the weather are due to, the 

 vertical circulation of the atmosphere, seems clear.f We have 



* "Two men," says Mr. M. A. Taylor, in a letter dated January 11th, 1860, 

 at Nueces, Texas, " "were actually frozen to death within a few miles of this 

 place this Avinter in a norther. Animals seem to tell by instinct when the 

 norther is coming, and make their way from the open prairies to tmiber and 

 other shelter, starting often on a run Avhen the heat is not oppressive. This is 

 when the change is to be sudden and violent. Many cattle, horses, and sheep 

 are frozen to death at sucli times." 



t Fwie Chapter XXI. 



