48 A. W. Greek/ — Geograpliy of the Air. 



any degree of correctness be asserted to prevail in the United 

 States. It is true that the prevaiUng surface winds of the greater ' 

 part of the United States come from the western quadrants — that 

 is, between southwest and northwest — and so are in substantial 

 harmony with the general atmospheric circulation as shown by 

 the upper- wind currents of Mount Washington (from the north- 

 west) and Pike's peak (from the southwest). But, apart from the 

 easterly and northeasterly trades on the Florida coast, it apjjears 

 from the records that in no case for any considerable section of 

 the country do 50 per cent of the winds blow, for any consecvi- 

 tive number of months, either from any single point or from two 

 neighboring points of the compass. Occasionally, however, the 

 local configuration of the country is such that winds are drawn 

 up or down valleys, and, being diverted from their free and 

 proper direction, the wind in such cases follows the trend of 

 the valley or depression. 



In general your Vice-President would feel inclined to refer 

 only casually to the work proceeding from the Bureau over which 

 he has the honor to preside, but this year has been marked by 

 special researches and investigations of general interest. As the 

 work of investigation has been entrusted to the professors of the 

 Signal Service, due credit should not be refused them from their 

 own official chief. 



Special reference should be made to the work of Professor 

 Charles F. Marvin, whose successful experiments on wind press- 

 ures and velocities have attracted the attention of experts both 

 in Europe and in this country. Unfortunately there was avail- 

 able only a small sum (about one hundred dollars) for the ex- 

 pense of experiments, but with this petty sum, supplemented by 

 his ingenuity, Professor Marvin has very satisfactorily determined 

 the coefficientsof the various forms of the Robinson anemometer, 

 Avith which instrument the velocity of the wind is very generally 

 determined. Following these investigations, the Royal Meteoro- 

 logical Society of England reopened the question, which, after a 

 costly set of experiments with results widely differing from those 

 of Professor Marvin, had been considered closed. 



The general results of these researches, which are believed to 

 be sufficiently definite for general questions, are not only prized 

 by the scientist, but they are of value to the engineer and the 

 builder. Indeed, to all interested in costly structures or extended 

 works liable to harm from Avind pressures, the factor of safety is 



