22 Land Magnetic Observations, 1911-13 



C. G. S. unit = 10"^ T; it would be necessary otherwise at times to round out 

 the observed vakie by one or more zeros. This is avoided by the use of the larger 

 unit; if the conditions under which an intensity result was obtained were such as 

 not to warrant publishing the fourth or fifth decimal, this is shown by stopping 

 with the decimal deemed certain. In general, however, as will be seen, the value 

 to the fifth decimal is given, but it should be understood that no claim is made for 

 the correctness in all cases of the last figure; it has been retained here primarily 

 in order that when all reductions to common epoch have been applied on account 

 of the magnetic variations, an error of a unit in the fourth decimal, due purely to 

 computation, will not enter. 



The first column in the table is headed "Station;" this gives the name of 

 place at which the magnetic elements were observed, the spelling adopted being 

 in accordance with the most reliable information at hand and conforming as far 

 as possible to local usage. The next column gives the geographical position, 

 latitudes and longitudes, as derived in most cases from the observers' local astro- 

 nomical observations following the methods already described. When the latitudes 

 are the results of fairly complete circummeridian observations of the Sun, or the 

 means of several reoccupations of the same station, or are derived from reliable 

 large-scale maps, then they are given to the nearest OM, though it should be 

 distinctly understood that this accuracy is not guaranteed, as even for these cases 

 the error may be as much as 0'.5 and even in some instances a whole minute of 

 arc. When the latitudes are given only to the nearest minute, there were either 

 no astronomical determinations or they may have been incomplete or defective; 

 these values are usually taken from standard atlases and for some regions may be 

 in error by several minutes. Owing to the numerous sources of error of a longitude 

 determination, and especially because of the uncertainty in more or less unexplored 

 countries of the adopted chronometer-correction on standard time, the longitude 

 in no instance is tabulated closer than to the nearest minute of arc. Usually it 

 is derived from the observers' astronomical observations. Considerable use was 

 also made of reliable large-scale maps, whenever available, and of standard atlases; 

 the values in regions but slightly surveyed may be out sometimes by several minutes. 



The date on which the magnetic observations were made will be found in the 

 fourth column. The following abbreviations have been adopted for the months 

 of the year: Jan, Feb, Mar, Apr, May, Jun, Jul, Aug, Sep, Oct, Nov, Dec. 

 The values of the magnetic elements will be found in the next columns as observed 

 at the local mean time, expressed to nearest 0.1 of an hour, opposite each value. 

 In cases where the observations which make up the mean value are numerous and 

 scattered over the various parts of the day, so that the mean may be practically 

 taken as the mean of day, the local mean times are replaced by the word "various." 

 Occasionally it has appeared desirable, where diurnal variation in declination was 

 observed or where numerous observations were made during a limited interval, to 

 give the local mean times of the beginning and of the end of the series and to 

 indicate the number of determinations from which the mean value is derived by a 

 number inclosed in parentheses: thus Q"".! to 11''. 3(7) is to be read "the mean 



