SERIES F.— EFFECT OP FOECE AND VELOCITY. 183 



SERIES P. 



The following table is designed to elucidate the last of the series of questions 

 proposed at the outset of this discussion, and shows the effect of combining the 

 element of force, or velocity, with that of time, in computing the mean direction of 

 the wind. The question itself is a highly important one, for since the real point 

 that we wish to arrive at is the mean direction and amount of the actual motion, 

 or transfer, of the air that passes over any given place or section of country, it is 

 obvious, that if there is a difference in the velocity of winds from the different 

 points of compass, or over different sections of country, such as to materially affect 

 the results that would be obtained if it were always and everywhere the same, all 

 the computations in the foregoing pages must require correction, if they be not 

 rendered in great measure worthless ; for they were all made on the assumption 

 that the velocity was uniform, or, which is the same thing, without any reference 

 to the velocity. And not only so, but nearly all the observations that have ever 

 been taken, both by land and sea, must be thrown aside (for in very few of them 

 has the force of the wind been recorded), and the whole work of observation must 

 be commenced anew. 



The question admits of being considered under two aspects: 1st, in regard to the 

 effect of difference in the mean velocities of winds from the different points of com- 

 pass, which obviously might affect both the direction and amount of the resultant, 

 at any given place of observation ; and 2d, a difference in the mean velocity of the 

 whole, in different regions or sections of country, which might affect the amount of 

 the resultant, but not its direction. Viewed in either aspect, the question is one 

 that can be determined only by observation and experiment. We can know no- 

 thing about it a priori. Difference of velocity may produce a very great effect 

 upon the mean resultant, or very little, or none at all. 



As, in the absence of anemometers, different meteorologists have employed differ- 

 ent measures for the velocity of the wind, some making use of the numbers them- 

 selves which represent the forces,^ instead of interpreting them into miles per hour, 

 as is done at the Smithsonian Institution, it seemed best, in examining the question, 

 to compare the results by each of these methods, with those for time only. The 

 data for the computations are contained in the columns of Series E, headed re- 

 spectively "Total Number of Observations," or Number of Hours;" "Sums of 

 Forces," or " Total of Numbers representing Forces ;" and " Integral Effect," or 

 " Total Number of Miles ;" and, for convenience of comparison, the resultants, both 

 in regard to direction and amount, are placed in parallel columns. In order to 

 express the ratio for time only, in terms of force and velocity, I first found, as in 

 former tables, the ratio that it bore to the total of the winds observed at the stations 

 (which must evidently hold true, whatever be the measure adopted for the velocity), 



* See Prof. Loomis's articles on the Meteorology of Hudson, Ohio, puhlished in the American Journal 

 of Science and Arts. 



