vi EDITORIAL NOTE 



For most of the stations averages of the series were computed by 

 the compilers of the data. For others they were computed by the 

 writer and his assistants. 



The means of the monthly sea-level pressures at the intersections of 

 10° lines of latitude and longitude were computed by Miss M. I. 

 Robinson and carefully checked. The data are classified by latitude 

 beginning with the Pole and proceeding toward the Equator. At each 

 latitude it is further classified by longitude beginning at i8o° W. and 

 proceeding eastward to 170° E. of Greenwich. 



The various meteorological offices and individuals have been very 

 helpful in notifying us of errors found in the printed data, and now 

 revised editions of volumes 79 and 90 are in print with these errors 

 corrected. It is hoped that this help in getting correct data will 

 continue. 



H. H. Clayton. 



