DISCUSSION AND ANALYSIS OF WINDS. 687 



In Texas the winds have nearly the same direction as in Arizona and New Mex- 

 ico, but the percentage of southerly winds in summer and northerly in whiter is 

 much greater. The winds in Texas have very strong monsoon features. This is 

 due in a great measure to the proximity of the Gulf of Mexico. The state, ex- 

 cept its extreme western part, is wholly open to the winds from the Gulf, and they 

 must be strongly drawn in towards the land in summer, as the continent is much 

 warmer than the sea. We have seen that there is a monsoon drawn in from the 

 small and narrow Gulf of California to supply the deficiency in the interior. We 

 must expect a much more powerful monsoon from the Gulf of Mexico. Winds 

 in Texas, other than S. and S. E., are all but excluded from April to September. 



In winter the winds are more northerly, but not N. E. or E. N. E. as in the 

 trade-wind regions of the same latitudes, but N. and N. W., i. e. winds blow from the 

 Staked Plain and other continental areas towards the Gulf of Mexico. Yet the 

 prevalence of these winds, if we take the number of observations only, is not so 

 great as that of the S. E. in summer. But the N. winds are extremely violent in 

 Texas ; they are the famous northers so well known and dreaded by seamen navi- 

 gating the Gulf of Mexico, and also by travellers in Texas, especially because of the 

 suddenness of their appearance. They are especially frequent in Central Southern 

 Texas, about San Antonio, while the north winds east of the Guadalupe River are 

 not so sudden and violent, resembling in fact rather the northwesters of the 

 eastern States. 



The cause of the violence of these winds must be sought to the southward in 

 eastern Mexico. This country has not as regular a climate, with small barometri- 

 cal variations, as other tropical regions of the same latitude. From December to 

 March there are frequent storm-centres, with low barometer, passing there, as also 

 on the eastern coast of Central America. A barometrical depression in Mexico or 

 southward of it must draw in the air from the interior of Texas and New Mexico, 

 where the pressure is high in the winter months. In April and May, when the 

 barometrical variations are less in Mexico, the northers are less frequent, and cease 

 altogether from June to September during the tropical rainy season, when baro- 

 metrical variation is. at minimum in Mexico. To illustrate this I give the mean 

 and extremes of the pressure of the air at Vera Cruz.^ (See also Plate 14.) 



Alean, Mean Min. Mean Max. 



January 30.10 29.86 30.36 



February 29.99 .68 .26 



March 93 .61 .33 



April 92 .64 .21 



May 86 .64 .09 



June 90 .73 .08 



July 96 .83 .06 



August 98 .85 .13 



September 30.00 .85 .12 



October 02 .t8 .20 



November 10 .19 .36 



December ....... .11 .78 .43 



' From the observations by Dr. Bcrendt, manuscript collection of the Smithsonian Institution. 



