INTRODUCTION. 



ORIGIN AND PREPARATION OF THE MEMOIR ON THE 

 WINDS OF THE GLOBE. 



CojSEvnJNicATED BY Pkofessok SELDEIST J. COrriK. 



The decease of Professor Coffin occurred before he had prepared any descriptive 

 text of this work, save what is given in the Preface, and therefore a monograph 

 found among his papers has special interest, as intimating the probable line of 

 treatment he would have pursued, and indicating topics of research in which he 

 was engaged, or to which his attention had been directed. It appears to be the 

 substance of a statement made to the National Academy of Sciences about two 

 years prior to his death. The title is, " A History of the Present Condition of an 

 Investigation of the Winds," Its contents, somewhat abridged, are as follows: — 



"This is not intended as a formal communication on the Winds, but rather a 

 brief narration of what I have accomplished, after having been engaged for many 

 years in the investigation of the laws that govern the circulation of the atmosphere 

 over the earth's surface, with the attendant phenomena. 



The following are the problems investigated:— 



1st. What is the mean direction of the wind over the different parts of the 

 earth's surface 1 Or in what direction does the air, as a whole, move over them "? 



2d. What is the progressive motion of the air in this mean direction 1 Or, if 

 data be wanting for determining this in miles — and we assume that the average 

 velocity of winds from all points of the compass is the same — during what propor- 

 tion of the time must the wind blow in this mean direction, so that if the remain- 

 der of the time were occupied by calms, or by winds whose conflicting movements 

 neutralize each other, the resulting general progressive motion of the air, as a 

 whole, would be the same as it now is 1 



3d. What is the direction and amount of the force that deflects the wind from 

 its mean annual direction in any given month, or season of the year 1 Or, in 

 other words, what must be the direction of a wind during any given month or 

 season of the year, and during what proportion of the time must it blow, so that 

 combined with the movement of the air in its mean annual direction, it may afi"ord 



(XV) 



