DISCUSSION AND ANALYSIS OF WINDS. 



The aim of Prof. Coffin in this work on the " Winds of the Globe," the reason 

 why he did not write the text, and how I came to take charge of this part of it, 

 has been akeady explained in the preface. 



In what way the ideas of the deceased author would have been modified by the 

 progress of theoretical meteorology in the last twenty years, as well as by the 

 much more extended knowledge of facts we possess now, it is impossible to say. 

 It is very likely, however, that he would have continued to rely principally on the 

 inductive method, would have avoided hasty generalizations, and would have 

 shown the same caution and candor as in his other works, omitting explanations 

 of what our present knowledge did not give sufficient data, rather than mislead 

 his readers. 



Before drawing the conclusions which seem to follow from the tables and maps 

 of this work, some explanations are necessary. 



The object of this work is to ascertain the movement of the air over different 

 parts of the earth's surface. For this purpose the mean direction and rate of 

 progress of the wind were calculated according to the formula of Lambert. It is 

 easy to see that to accomplish this with precision, we should know the velocity of 

 the wind at all places at which calculations are to be made. Now we know 

 the velocity of the winds in a somewhat accurate manner only for a very small 

 number of stations. For many more the velocity of the wind was merely esti- 

 mated, and for a majority of places, the direction of the wind alone is known. 

 Now the progressive movement of the air over a certain place, even taking into 

 account the direction only, without considering the number of miles travelled, 

 can be .ascertained from the number of observations alone if we make the suppo- 

 sition that all winds have the same velocity; but this is obviously not the case. 

 In nearly all known instances where the velocity of the winds has been ascertained, 

 it has been found to vary considerably ; generally, the more accurate observations 

 with self-registering anemometers give a greater difference between the velocities 

 belonging to different directions of the winds than mere estimates have given, the 

 difference being seldom less than 1 to 2, and sometimes even 1 to 4 or 1 to 5. 



In considering attentively the observations for the stations where the number 

 of observations, for hours, and the velocity are given, it is seen that generally the 

 most frequent wind is also the strongest, or, comparing the mean direction of the 

 wind calculated from the number of observations only, with that obtained by 



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