INTEODUCTION. 



This memoir is an expansion of a report on the winds of North America and 

 the North Atlantic Ocean, prepared in obedience to a request of the American 

 Association for the Advancement of Science, and read at its meeting in Philadel- 

 phia in 1848. Although the northern portion of the eastern continent did not 

 properly fall within the limits of the report, yet it was thought that it would be 

 more complete if it could be made to include the entire northern hemisphere; and 

 this has been done partly through the aid of American missionaries and others 

 residing abroad, who kindly sent manuscript records of their observations, and 

 partly through meteorological registers published in different European journals, &c. 

 In this way, I have been enabled to obtain a large amount of material from Europe, 

 Asia, Northern and Western Africa, and several islands in the Atlantic and Pacific 

 Oceans. With a view to obtain more full data at sea, I made arrangements, through 

 the aid of a friend in New York, to procure from shipowners in that city the loan 

 of a number of log-books kept during voyages in the Atlantic and elsewhere. 

 From these, and other sources, I had collected records of observations at sea for 

 periods amounting in the aggregate to between six and seven years, when, learning 

 that Lieut. Maury, of the National Observatory, was successfully j)rosecuting the 

 same work under far greater advantages, I relinquished that field, and confined 

 myself to observations on land. 



An interval of several years which has elapsed since the memoir was first pre- 

 sented to the Smithsonian Institution, while it may have rendered some parts less 

 valuable, has enabled me to improve others by the addition of new matter derived 

 from the Smithsonian operations, and those of the National Observatory. Among 

 the materials obtained from the latter may be mentioned, a collection of observations 

 at sea, amounting in the aggregate to a period of more than one hundred and 

 twenty years. I may also mention, as an important addition, the discovery of 

 systems of deflecting forces on both sides of the Atlantic. 



My acknowledgments are due to the following gentlemen for the aid they have 

 rendered me in obtaining the data necessary for the investigation, either by con- 

 tributing their own observations, or affording facilities for procuring those of 

 others : — 



