638 WINDS OF THE GLOBE. 



Smithsonian Institution.' Few of the observers possessing anemometers, the 

 velocities were usually estimated in force numbers, which were reduced to miles 

 per hour on the following scale : — 



1. Yei-y light breeze . 



2. Gentle breeze 



3. Fresh breeze . 



4. Strong wind . 



5. High wind 



6. Gale . . 



7. Strong gale 



8. Violent gale . 



9. Hurricane 



10. Most violent hurricane 



2 miles per hour 



4 

 12 



25 

 35 

 45 

 GO 

 T5 

 110 

 100 



' [From a monograph found among my father's unpublished writings, I extract the following 

 statement in reference to these Velocity Tables, which were then incomplete, being in course of 

 computation. — Selden J. Coffin. J 



"In the Winds of the Northern Hemisphere, 1853, this question was discussed, so far as the 

 comparatively meagre data then at my command allowed, and the conclusion arrived at was, that, as 

 a general thing, this difference of velocity, while it increases the magnitude of the resultant, does not 

 appreciably affect its direction. The data on this continent from which I reached the above con- 

 clusion, consisted of observations taken at 103 different places, for an aggregate period of 397 months, 

 or about 33 years, more than half of them being from Eastern and Middle States, and only an aggre- 

 gate of about two years from States and Territories west of Ohio. 



"In 1857, the Secretary of the Smithsonian Institution ordered a thorough and exhaustive discus- 

 sion of the subject, based on the observations reported to the Institution for the years 1854-7, from 

 418 different places on this continent, for an aggregate period of 8589 months, or over 700 years, in 

 which each observer noted the direction of the wind, usually three times a day, and affi.xed to each 

 record a number from to 10 to represent the velocity, according to the scale given above, based on 

 the experiments of Rouse and Smeaton. 



" The method of discussion was, first to group the places of observation into districts of moderate 

 geographical extent, then to compute, for each district, the mean velocity of the winds, as estimated 

 by the observers, both the lower current and that indicated by the motion of the clouds, for each of 

 the eight principal points of the compass, for each season of the year, and for the whole year, 

 counting all winds between the N. and E. points as northeast, those between S. and E. as southeast, 

 etc., and finally to compute the resultant motion of each of the two currents, over each district, for 

 each season of the year and the whole year, first from the actual motion estimated as above, and then, 

 for the purpose of comparison, on the supposition that the winds from all directions moved with the 

 same mean velocity. To carry out this plan required great labor, inasmuch as beside classifying 

 the winds according to the points of the compass from which they came, the record of the estimated 

 velocity at each separate observation, amounting in the aggregate to over three-fourths of a million, 

 had to be translated into linear distance, or miles per hour. An aggregate of over 5 years of work- 

 ing time has been spent upon it. The work of classification was performed chiefly by ladies ; that 

 of translating into miles, which required only care and accuracy in applying the scale and summing 

 up the results, by men competent for such work ; while the trigonometrical resultants were mostly 

 computed by Robert A. CofBn. 



" The results corroborate the views advanced in The Winds of the Northern Hemisphere in regard 

 to the magnitude of the resultants, but not in regard to their direction, both of which facts will 

 appear from the following general statements, in which it will be seen that the effect of difference in 

 velocity is to throw the resultant northerly far morg frequently than southerly, and at a much greater 

 angle ; that it increases its magnitude far more frequently than it diminishes it, and by a greater 

 amount. 



"In 10 districts north of the 45th parallel of latitude it is thrown northerly ; in 9 at an average 



