204 CARNEGIK INSTITUTION 



to mind, it is unnecessary to dwell at greater length upon the prac- 

 tical and theoretical importance of this problem. No magnetic data 

 have been obtained on the ocean areas since the advent of iron ships, 

 except from occasional expeditions. Our present lines of equal 

 magnetic declination over these waters depend almost entirely upon 

 the data acquired in wooden ships, fifty to one hundred years ago. 



{b) International observatio?is of the variations. — An exhaustive 

 study of the numerous variations of the earth's magnetism and 

 electricity can be successfully pursued only by international co- 

 operation under the direction of a central or international bureau, 

 so as to secure uniformity in observation and reduction, and to 

 insure the prompt coordination and publication of results. All 

 past international work, as, for example, that conducted by many 

 nations during the international "polar year" of i882-'83, has 

 suffered from the lack of a central or head bureau. During that 

 year thousands of observations were made ; the full utilization of 

 those has not j^et taken place, although the}' were made twenty 

 years ago. Again, the remarkable activity now manifested over 

 the "entire globe is not being guided by any one internationally 

 recognized bureau ; we may therefore expect that, after the obser- 

 vations are made, it will be many years before the results of this 

 vast amount of work will be known. Printed international forms 

 for guidance in observation, reduction, and publication would pre- 

 vent much waste of effort. 



Under this heading is also embraced the establishment of secular 

 variation or repeat stations throughout the globe, at which mag- 

 netic observations would be repeated at regular intervals, and thus 

 make it possible to obtain the data necessary to keep magnetic maps 

 ever up to date in all regions. The desultory waj^ in which such 

 observations have been made in the past has resulted in an irrecov- 

 erable loss to science. 



(f) Observations iri oceayi depths aiid atmospheric regions . — As long 

 as observations are confined to the surface of the earth, the actual 

 distribution of its magnetism and electricity will never be known. 

 The unequivocal solution of the problem demands observations in 

 the waters below and in the air above. The first step consists in 

 devising the proper instruments. 



Other problems, such as the correlation of local and regional dis- 

 turbances of the magnetic needle with geological and physiographic 

 features, and the correlation of magnetic and electric disturbances 

 with meteorological phenomena, might be mentioned. 



