^,- PREFACE. 



winds made at 3223 different stations on land, and during numerous voyages at 

 sea, extending from the parallel of 83° 16' north latitude, to beyond the parallel 

 of 75° south latitude (the extreme points ever reached by man) altogether embrac- 

 ing an aggregate period of over 18,500 years. 



"The stations on land are distributed over its surface as follows: — 



Number of stations. Aggregate number of years. 



America 2077 over 12,3S0 



Europe 740 " 4,180 



Asia 244 496 



Africa '7C 1^1 



Islands of the sea' . . . . S6 314 



"Of these stations in .America, about 1900 are within the limits of the United 

 States, viz., over 1400 which reported to the Smithsonian Institution between the 

 begiiming of the year 1854 and the end of 1869, over 300 military posts that 

 reported to the Surgeon-General of the United States Army, and some 100 to 150 

 other places. The observations at the military posts embrace all that were reported 

 from the commencement of the system in the year 1822 up to the end of 1859, 

 together with those at posts west of the Mississippi for the succeeding ten years 

 also, or up to the end of 1869. 



"At sea, between the parallels of latitude 60° north and 60° south, the observa- 

 tions are mostly taken from the Wind and Current Charts prepared at the United 

 States Naval Observatory, under the direction of Capt. M. F. Maury, which cover 

 the entire Atlantic, Indian and South Pacific Oceans, and all of the North Pacific 

 except a comparatively small portion, the completion of which is much to be desired, 

 lying between the meridians of 150° east and 165° west from Greenwich; and 

 nearly every square of 5° in latitude by 5° in longitude is more or less fully repre- 

 sented. For the Arctic and Antarctic Oceans, and the Mediterranean, Black and 

 Red Seas, the material is derived mostly from other sources. The observations on 

 the ocean embrace a total of a little more than one thousand years. 



" The whole material is arranged in the form of tabular series, which require no 

 explanation beyond what is given in the headings of the several columns ; and for 

 more ready reference to the data from any particular place, or group of places, as 

 contained in the tables, as well as with a view to a more scientific arrangement of 

 the whole, and for convenience in the discussion, the entire surface of the earth is 

 conceived to be divided into 36 zones by parallels of latitude drawn 5° asunder, 

 commencing at the north pole, and proceeding southerly ; and in each zone the 

 places of observation are arranged in the order of their longitudes, commencing at 

 the 180th meridian from Greenwich, and proceeding easterly. 



" The method of reduction is the same throughout as in my former work. Instead 

 of giving the prevailing direction, or that point or points of the compass from which 

 the winds blow most frequently, and rejecting all the rest, the traverse of the whole 

 is resolved, in the same manner as that of a ship at sea. The former method, which 

 was once almost the universal one, and which still finds advocates, may be useful 



' Including Australia and Greenland. 



