JANUABT 13, 1911] 



SCIENCE 



45 



occurred during the years 1882-1909. No. 

 1 of these is the unique magnetic disturb- 

 ance of May 8, 1902, which, as far as can 

 be ascertained, occurred simultaneously 

 with the destructive eruption of Mont 

 Pele. On account of this interesting co- 

 incidence the records of twenty-five observ- 

 atories in different parts of the world were 

 collected and studied in my office. When 

 the various scalings of the time of begin- 

 ning of the disturbance were put together, 

 they appeared to increase to the east, the 

 effect apparently having been recorded 

 first in Europe, next in Asia and last in 

 America. The speed of progression was 

 such that a continuous circuit of the earth 

 around a great circle would require nearly 

 4 minutes, or in other words, the velocity 

 was on the order of 100 miles per second 

 or only about one two-thousandth that of 

 light. 



No. 2 — the disturbance of January 26, 

 1903 — was one investigated by the eminent 

 physicist-magnetieian Birkeland, the au- 

 thor of the cathode ray theory of magnetic 

 disturbances. For this again an easterly 

 progression, on the same order as for No. 

 1, was found. 



Next, Nos. 3-19 are 17 storms between 

 1882-89 which were investigated by Will- 

 iam Ellis, who was for a half-century in 

 charge of the magnetic work at Greenwich. 



The nineteen cases thus far mentioned 

 showed a remarkable consistency in the 

 direction in which the times increased, 

 viz., to the eastward, only one sixth show- 

 ing the reverse direction. 



In order to test this result further with 

 the aid of the best data immediately avail- 

 able, Mr. R. L. Faris, Inspector of Mag- 

 netic Work of the United States Coast and 

 Geodetic Survey, undertook, at my re- 

 quest, a special examination of fifteen sud- 

 den storms between 1906 and 1909. He 

 had to restrict himself for the time being 



to the five magnetic observatories belong- 

 ing to the United States, viz., Cheltenham 

 (Maryland), Porto Rico, Baldwin (Kan- 

 sas), Sitka and Honolulu, which extend 

 over about one quadrant of the earth. Mr. 

 Faris scaled the times of beginning with 

 every possible care; he estimated that the 

 error of measurement was about one half 

 minute and certainly not over one minute. 

 Yet the individual observatories differed 

 by quantities ranging from 1.1 to 6.7 

 minutes ! Here again, for 10 out of 15 

 cases, the direction of progression, over the 

 limited portion of the earth embraced, was 

 eastward, and for only one third was it 

 westward. 



The next foiir cases are some tiny pre- 

 liminary disturbances preceding larger 

 ones, investigated by the director of the 

 Zi-ka-wei Magnetic Observatory, Father 

 J. de Moidrey, and by Mr. Faris ; for two 

 of these the direction of progression was 

 east, and for two, west. 



Summarizing — for 28 out of the 38 

 cases the times of beginning increased east- 

 ward and for but 10, or about one fourth, 

 the increase was in the reverse direction. 

 The following conclusion was accordingly 

 drawn : 



Magnetic storms do not begin at pre- 

 cisely the same instant all over the earth. 

 The abruptly beginning ones, in which the 

 effects are in general small, appear to 

 progress over the earth more often east- 

 ivard though also at times westward, at a 

 speed of about 100 to 200 kilometers per 

 second, so that if a complete circuit of the 

 earth were made it would require, on the 

 average, between 7 and 3 minutes. 



DIRECTION OF MOTION OF MAGNETIC 

 DISTUEBANCES 



If it is a fact that magnetic disturbances 

 are propagated more decidedly in one 

 direction than another and that they dif- 



